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Making silicone molds...

Posted by Buddyfly (My Page) on
Tue, Sep 9, 03 at 1:13

Does anyone have experience with making silicone molds? I have made one from a leaf and it turned out perfect. Then I made a plaster of paris mold from it. Do you think if I put silicone on the plaster of paris mold that it would totally stick to the plaster? What if I sprayed the plaster with a release agent first? I'm wondering if I can use the plaster mold to make many more silicone molds of the same leaf.

I have also tried making silicone molds from an earring and ruined the earring as the silicone stuck to it and it wasn't going to give up the battle. Also ruined a vase this way! I'm learning... thank goodness it was with things I wasn't that crazy about. Would it have worked if I had use a silicone spray on the object first?

Also, has anyone ever made a mold from a fresh flower. I'm wondering if I could make a silicone mold from a morning glory bloom. Any advice would be really appreciated!

Buddyfly


Follow-Up Postings:

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RE: Making silicone molds...

I'm playing with silicone caulk as a molding material as well. In a book I have about molding it suggests using a thin film of petroleum jelly as a release agent. If I read correctly, you made a negative mold out of silicone then a positive out of plaster? I've sucessfully done a silcone negative mold from a cement leaf casting, then re-used this to cast additional leaves. I also tried making a plaster mold of a leaf backside in which I intend to may a silicone negative out of next. The plaster casting of the leaf back side shows extreme detail and has no inperfections from sugar reaction. However, the standard mix is to runny and seeped around the leaf edges. Does anyone know if you can use less water in the plaster mix to make it thicker and yet have it cure properly? I don't know about the morning glory bloom idea. The flower would colapse under the weight of any molding material I would think.
Leigh


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RE: Making silicone molds...

Good morning Leigh!

I made a silicone casting from the back of a leaf then made the plaster of paris casting from the silicone mold. Positive, negative... these are terms I guess I better start understanding, eh? Canadian here!

I have taken pictures of the process. One thing I was wondering if I could do as well is ... could I use a release agent on the plaster of paris mold I've made and use it as a 'stamp' to put an impression on a cement or tufa stepping stone. I wondered if it would leave a detailed impression. I thought of this when I read about people putting impressions of their children's hands in the top of a stepping stone. Anyone have any ideas about this stamping idea... whether it will work?

Re morning glory Leigh, I've read that you can make a support out of wet sand packed into the shape of the item you desire to cast a tufa of. So I was thinking of making that sand 'well' to pop a mg bloom into and then make the casting of it. The problem I am having is trying to find an agent that is fluid enough and quick setting enough that it won't wrinkle the bloom.

So many ideas and so little time to play with my projects! Reality bites! lol

Buddyfly


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RE: Making silicone molds...

OK, I just gave it a shot to try a morning glory mold. I held up an open bloom in the bottom of a bowl and poured dry sand until it came to just under the tips of the edges of the bloom. Then, using a caulking gun I squeezed out a stream of silicone and started in the funnel center. Then I went in a spiral, round and round until the entire bloom was covered in silicone. Now I will just set it aside and let it fully harden for 24 hours and see what I get. The weird thing was that as I was adding the silicone, the blue flower was turning a fushia pink!! Chemical reaction I guess but it was neat to watch!

B.


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RE: Making silicone molds...

Wow! Sounds like you might have done it! Keep us posted on this one. I also updated the Decoupaged leaf & silicone mold report posting with pics and reports of where I'm at. May be of help to you, and please help me if you recoginize whats going wrong with my plaster thing. I think doing the cement casting on a latex mold is better than cement casting on plaster because the latex is flexible (and won't break under press applying cement!)
Leigh


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RE: Making silicone molds...

I heard that you should use paste wax to seal the plaster then use a release agent.

Josie


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RE: Making silicone molds...

OK, thanks for the ideas coming in and please keep them coming! I think that paste wax and release agent makes sense. The plaster of paris is so porous that it will need a sealing of some sort. Paste wax would absorb into the plaster and not affect the detail. Might try that! You don't remember where you read that do you Josie?

B.


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RE: Making silicone molds...

I don't remember where I read the original suggestion but when I looked up "concrete molds" on eBay I came up with someone who is selling (6) pamphlets (plus 1 freebie) that mentions car wax and I am assuming they mean to use it on plaster molds. It's kind of pricey at $14.95 (isn't that the price of some softcover books!?) but I still may spring for it as they only have 3 neg. feedbacks out of 883 & it does come with a moneyback guarantee. I guess the old adage of marketing bears true here; "the market will only bear what the consumer is willing to pay". And they are a payin'.

Their ad states:

Basic Moldmaking guide takes you through the steps of creating your very own stepping stone mold, rock molds and basket molds using latex rubber. How to apply the rubber compound, how to create forms for a backup shell, how to deal with undercuts, what car wax is used for, how to use your liquid fiberglass, fiberglass screening and much more. Create molds for concrete, soaps, plaster and more.

Josie

Here is a link that might be useful: How To - Make Lawn Ornaments, Rocks & More


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RE: Making silicone molds...

Here's a link to a book I got on mold making. I find it an excellent resource, easy to follow instructions and great pics of the process.

http://www.amazon.com/exec/obidos/tg/detail/-/1558701281/ref=pd_bxgy_text_1/002-2088565-7724821?v=glance&s=books&st=*
Leigh


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RE: Making silicone molds...

Somewhere in all the books, articles and websites I've read in the past month, someone said to coat plaster of paris molds with shellac before using. This would seal the plaster and then you could use a release agent. Shellac is used extensively in finishing techniques between layers of disparate & incompatible products (water-based to urethane, for instance), so sounded plausible to me.


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RE: Making silicone molds...

Hi,

If you are working with latex, an excellent releasing agent is murphy's oil soap. Just take a sponge, wet it, put on some murphy's then lather it and rub all over the mold. When it's dry you can cast in many mediums including plaster or cement w/o a problem. Another release agent for plaster is PAM cooking spray. Also, if you are working with a plaster mother mold soak it in water before you pour plaster in it for your casting, it will act as a release agent. Using paste wax or shellac will give your plaster mother mold a flawless casting since it will cover up minor imperfections. Have fun.


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Some molds I have been working on....

Here is my kitchen table at the moment! lol As you can see I have many experiments on the go. There are plaster of paris molds and silicone molds made from the plaster molds. Right at the moment I am experimenting with release agents to see which works best. The hardest time I am having is being patient and waiting for the 'paris' to dry totally. If I try to make a silicone mold too soon with it, it removes a slight powdery coating from the 'paris' mold. If I wait until it is totally dry and use a release agent, it comes off clean.

B.



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My face in 'paris'

LOL... this one was fun and... PAINFUL!! I made a 'paris' cast of my face after coating my face with vaseline. It came off ok... all except for my eyelashes on one eye. Totally STUCK to the lashes! Had to pull them out and MAN! did that hurt! On top of that the mold had some holes in it. I will try to repair it. If that works, great. If it doesn't work, I will try casting another one. The 'paris' thickens so quickly and its hard to get the face all properly coated. I even had a friend some over to pour the plaster on my face. She now understands what I mean when I say to "work very quickly"!! Most of the plaster ended up in the garbage because it hardened on her.

So, here is the 'holey' results! By the way, you are looking INTO the mold. The way the picture came out, it looks like it is 3D. Weird how that happens. At least I can see how my tufa face might turn out if I ever get this whole experimenting business over with! lol

B.


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And here is the repaired one...


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RE: Making silicone molds...

Hi, Buddyfly,

You're doing some interesting experiments with good looking results. Thanks for sharing with everyone. Would you mind a few questions?

When you make a silicone mold of a leaf, how many coats/layers of silicone do you use? Do you brush it on? Do you put any kind of release agent on the leaf?

When you make a plaster casting in a silicone mold, what kind of release agent have you found works best?

When you make a silicone mold of a plaster casting, do you apply a release agent to both the casting and the mold? Which release agent works best?

Thanks,
Eva


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RE: Your Face in 'paris'

Forgot to mention that your face casting, even though painful, turned out great!

Eva


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RE: Making silicone molds...

Eva... I had lots of questions too before I started. I'm trying everything in an experimental mode. I've used paste wax on the plaster mold... it worked ok.. a lot of wax came off with the silicone. Then I tried car wax... same thing but it was easier to apply because it was liquid. Tried vaseline and it released ok, it just lost some of the detail. I am currently trying water as the release agent. I took a cured plaster leaf and ran it under water a couple of times quickly. The water soaked in immediately. Then I quickly applied the silicone. Will see how that one goes.

I'll try to answer some of your other questions next time I post, ok? I have to think about some of the things I have tried. Want to get it all straight.

Take care!

Buddyfly


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RE: Making silicone molds...

Great Work Buddyfly!! WOW wish I had the patience to experiment....Keep it up everything looks great! Anela


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Anela...

Thanks Anela! That's ok, I'll keep experimenting, and you keep making dinosaurs! Especially Ducky! Yup, yup, yup!

LOL

Buddyfly


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RE: Making silicone molds...

Buddyfly,
What kind of or name of the silicone product? The face piece is really great! I have a couple of plaster faces that I made with son and daughter, however the mouth and eyes are not there, it really is more of a mask. It was with their 5th grade classes, then they were painted with acrylics. I like yours lots and lots with the lips eye lids and eyes so detailed. I have some plaster bandages maybe the kids would like to keep me quiet for a little while. hmmmm. Dena


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RE: Making silicone molds...

Buddyfly,
I had read in a molding book that you should NEVER use plaster of paris for molding body parts. The reason being, as plaster of paris cures it "heats up" and can cause burns. Did this get overly warm or is this warning an err on the safe side suggestion? I've felt curing plaster of paris at different stages and didn't feel it was all that warm on the outside and wondered about this. My silicone molds are not as good as I was hoping. The silicone is not getting into the vein of the leave as well as I'd like. The vein is kinda roller coaster looking. I'm just not getting the silicone pushed into the pattern as well as it should. By the way, silicone is on sale at Ace Hardware here for $1.99 a tube (reg. 3.24). Good time to try guys!
I also found a website where they sell a catalyst that speeds up the cure, and has a little description of thinning the silicone with naphtha to get a good base detail. I have it bookmarked at work and will add a link later today.
Leigh


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RE: Making silicone molds...

Leigh, I would LOVE to know about a thinner for silicone! I was wondering about that very thing. Naptha! Looking forward to that link.

As to the heat... no it never got hot at all. In fact I felt like I was at a spa! I loved it! My skin felt great after the whole process. You put vaseline all over your skin to help as the release agent and I suppose as a barrier from actual contact with the plaster. I am constantly working with plaster of paris with my bare hands and have never gotten any reactions to it. Why don't you try it on yourself according to the link I gave earlier. Then you will know how safe it really is. Just remember to put a LOT of vaseline over the eyelashes, eyebrows and any facial hair!!

B.


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RE: Making silicone molds...

Sorry it took so long to get back. Below is the link to a taxidermy guy's site that talks about thinning with naptha
(50%) and using his catalyst. Haven't tried yet, bought the naphtha and will do tomorrow (day off yeah!). The naphtha sounds like some heavy duty stuff with a lot of precausions on using it. Here's some reading material for now, and I'll post more detail later. (Posting this same message on both molding threads)
Leigh

Here is a link that might be useful: Silicone Catalyst


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RE: Making silicone molds...

Hi again Leigh, I 'devoured' that link! lol Going to pick up some naphtha too. Just going to get a small amount to get started. I will only do the lining of the item to be molded and then I will use the regular full thickness of silicone to thicken the mold. I'm including a link for you... it's an amazing chart that I printed out for quick reference. The one column gives you the item you wish to make a mold from, the next colums suggests what to use to make a mold and the third column gives you suggested release agents to coat your item being molded. I hope you find it as useful as I have already. I found it by doing a Google search: +naphtha +"silicone thinner" I wanted to see what other sites said about using naphtha for a thinner and I came across this chart.

Enjoy your day off tomorrow. I'm going to to outside and collect a few more leaves from my garden and make some more paris molds.

Looking forward to hearing how the naphtha experiment goes for you!

Buddyfly

Here is a link that might be useful: Reference Chart for Mold Making


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RE: Making silicone molds...

A good release agent between plaster & silicone is petroleum jelly thinned with paint thinner (2 parts petroleum jelly to 1 part thinner). The thinner will evaporate leaving a very thin coating of jelly. Store your mixture in a small jar & use with very good ventilation.

Josie


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RE: Making silicone molds...

I did put pictures of the plaster bandage masks that I made with the kids each when they were in 5th grade.
Use the arrows to go forward to see all three. Last photo on page 3 of this album shows the plaster hand, done from an alginate mold. Another fun mold making medium.
I really do love the plaster face, and am thinking how I can get my dad in on this, his face has so much character. I wonder if he would notice if I started the process while he was asleep!:) dena

Here is a link that might be useful: plaster bandage face masks


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Re Vaseline and Paint thinner

Thank you Ditzzy for that recipe for the vaseline release! That was interesting about how it evaporates. Makes sense to me. I'll try that for sure. I believe I have some paint thinner (turpentine will do I assume??) and must give it a try. I tried straight vaseline and I lost a lot of detail. Would you say you could BRUSH on the vaseline/thinner onto the plaster mold? If it will be thin like water, then I suppose a small paint brush would be the best method of application.

Anxious to try this but will wait until tomorrow now. Getting kinda late! lol

Thanks again!

Buddyfly


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RE: Making silicone molds...

Dena, that hand was amazing in the detail! Loved it! I read some instructions on a website somewhere in my many searches about this topic ... about making plaster of paris molds. They said to put the release agent on your item you want to make a mold of. Pour p. of paris in a plastic container just big enough to hold the full item. Just pour the container half full. Set the item in the wet p. of paris, top pointing down, and sink it in half way. Let it set until totally hard and dry. Then you put vaseline on the dry surface of the p. of paris. Make up some more wet p. of paris and pour it over top of the item being molded. Fill up the plastic container just up to the very bottom of the item you are casting the mold of. Let it cure hard again. When it is totally dry, you should be able to separate the two pieces of plaster of paris, removing the object from the center. To make a copy of it, paint your release agent on the inside of the two pieces of mold. Put them together again and duct tape them together. Pour your casting material in the hole that will be at the top. Use whatever product you want... tufa, plaster, cement, etc. Let it set and remove tape and unmold.

Did that make sense? lol... I'm glad I typed it out... it helps me to have it clear in my mind when I go to make a mold like this. I might try my hand as a mold. Will take a long while of sitting with my hand totally still. But at least it will be a re-useable mold.

I can see your 'hands' in a tufa project. I visualize making a bird feeder with the hand or two hands holding the container, or you could mold your hand with a finger held up like a perch for the birds to land on! Here I go with my imagination again! It's a curse! lol

Buddyfly


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RE: Making silicone molds...

Dena,
That hand made of alginate has amazing detail! I've read where alginate is quite expensive, how much did you have to use (or dollar estimate?). Keep us posted on the plaster bandage face masks including the eyes, the ones of your kids are great!
Buddyfly,
As you do your two part mold, please post pics of the different stages.
Leigh


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RE: Making silicone molds...

Buddyfly,
You can only do the p of paris mold that you are describing with an item that has no undercuts, so you could possible do a flat sort of hand or one that is everso slightly cupped, but no like the hand that I have holding the mask, you would not be able to get your hand out. Plaster begins it set up process by some shrinking and quickly hardening with no wiggle factor occuring. Just mention this as a caution to really think through what you are molding. Your description of the two part mold is accurate and easy to follow. I have not done a two part mold, and my hand (according to the art teacher) would require three or more parts to the mold, so it will not be done by me!
If you are doing your own hand it helps to have someone else with you in this process to do the mixing and pouring.

Leigh,
The art teacher at the highschool purchased it in a fairly big quantity. We used a liter pop bottle with the top portion cut off so it was just a tube with a bottom, then a 2" collar was made out of cardboard and taped to the top of the liter tube, to hold the portion that becomes the base of the hand. The person who was doing their hand had to figure out what they wanted their hand to do while in the alginate. So lots of hand movements were happening, the only criteria for the highschool teacher was that any obscene gestures or gang signals would be disposed of and the student would face some consequence.....Since the hand can not be seen when in the alginate, this was also a trust exercise.
The alginate was a powder purchased at a pottery supply store, I think it was sort of expensive but do not know the exact price. My portion I paid 10 to do this project, and I wanted to learn it. I think each hand took about 2 cups of alginate and was mixed with an electric hand mixer or could be done in a blender with cool water, the warmer the water the faster it sets up. It is kind of glumpy looking. Once the right consistency, it was poured into the liter tube to just below the bottom of the beginning of the cardboard collar. Then the hand (a dampened hand worked best, was positioned into the alginate, without touching the bottom or the sides of the liter tube. The hand model had to hold still for 3-5 minutes, that is sort of hard, our hand has a lot of reflex nerves in it. Once you could kind of touch the top of the alginate and it bounced it was time to gently wiggled out of the alginate. It felt kind of like being stuck in soggy sand and tended to want to suck the hand back. Plaster of paris was mixed up slightly thinner than usual and then poured into the alginate mold, and to the top of the cardboard collar. This was allowed to sit for three days. (they did it on a Friday, and undid theirs on Monday. The alginate portion is already beginning to shrink in a few days, so it easily released from the liter tube and the alginate was cut and peeled away, leaving a very detailed hand, every hair on my knuckles (not many) showed. hope this makes sense. Dena


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Silicone caulk and naptha (thinner)

I've been following your conversations on this and did a little Yahoo search usine "silicone caulk" "mold" and "thinning"--one of the first links was to this message. Thought you might find it interesting. Naptha is "lighter fluid"!! ...at least according to this guy and it seems like they may have been experimenting with this theory also. It's on another group forum and you'll have to have signup privileges if you're interested. I can't display the link so you'll have to do the search yourself and see what I mean.


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another thinning agent for silicone caulk

ok...so I'm looking at one of the next search links down and this person says you can thin silicone caulk with distilled water--better yet--a little less toxic if it works.


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silicone caulk thinning agents

I saw another reference to lighter fluid but it was "charcoal lighter fluid" this time. I also saw mineral spirits referenced as a thinner.


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RE: Making silicone molds...

OK, I just tried the thinned petroleum jelly on my plaster of paris leaf mold. It did thin nicely and was able to apply it with a paint brush. The problem I had was now the silicone won't stay put when I try to spread it over the mold!!! It keeps lifting off. Grrrr! Not liking experimenting tonight!

Leigh... where are you? How did your experimenting go today??

Buddyfly


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RE: Making silicone molds...

Buddyfly,
Here I am! Did get some experimenting done yesterday. I thinned petroleum jelly with the naphtha and brushed it on a plaster of paris mold and a stained and sealed leaf casting.
Went on really nice and thin. It makes sense that this is lighter fluid basically, cause its suppose to evaporate and leave just the jelly. I then thinned the silicone with naphtha (50% by volume) and brushed it on the plaster mold. Went on very nicely. I squirted a dollop of caulk straight from the tube onto the jelly coated leaf casting. After an hour, the dollop lifted right off. The coated plaster mold however, was still in the tacky stage and I couldnt lift an edge. The thinning does slow down the cure time. Im hoping this is not a result of brushing the thinned silicone on right after the jelly coat (didnt allow enough time for the naphtha to evaporate from the jelly?). Im hoping it wont matter because of the naphtha being mixed into both products. Anyway, will leave til tonight and add the full strength thickness to build up the mold. If this thinning gives you the fine detail but adds to the curing time, I think Ill order the silicone catalyst.


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RE: Making silicone molds...

Leigh, that is very interesting. I expected that the curing time with the naphtha would be longer, but I'm willing ot live with that. I'll just figure the extra time into the whole thing. When you lift off the cured silicone from the plaster of paris mold, did it come off easily?? Did you use a release agent?

I've been putting thick silicone directly on the cured plaster of paris mold withOUT a release agent. You really have to pull on it to get it off but it comes off without ripping or stretching! I did a strawberry leaf last night in this fashion. Good detail.

I am really wanting to practice all this mold making and the different release agents because I want to cast my face mask soon and I don't want to have anything go wrong. I don't want to have to lose any more eyelashes! lol

Buddyfly


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RE: Making silicone molds...

Buddyfly,
I had used the petroleum jelly thinned with naphtha as a release agent on the plaster mold. After applying that with a brush (went on nice and thin), I mixed silicone with naphtha (50%) and brushed a thin coat of that onto the plaster mold. This was probably only a 5 minute wait time in between so I'm not sure if the naphtha had enough time to evaporate and don't know yet if that will be a problem. I peeled up a little on the edge this morning and it seemed to be lifting okay but didn't want to risk tearing it by trying to lift a large section. Will be adding the "strength" layer of silicone right out of the tube and am afraid I won't have much else to report until that cures (I leave it go 3 days usually.) It's payday today so I'll get some catalyst on order this weekend.
You mentioned you couldn't get the silicone to stay put on top of the thinned petroleum jelly release layer. Were you using silicone right out of the tube or thinned down? Straight out of the tube it is hard to manage and I think the jelly causes it to slide (doing it's job as a release agent!) The thinned version I used brushed on easily.
Leigh


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RE: Making silicone molds...

OK, I've just finished casting my first attempt at a face from my plaster mask that I made. I'm very anxious to see what happens tomorrow when I attempt to unmold it. I just hope it RELEASES from the mask! I might want to re-use the mask for another project.

Buddyfly


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RE: Making silicone molds...

With all the discussion in this thread, I am a bit lost. Buddyfly, what is it that you did to treat your plaster mask? And what type of casting material did you try? Looking forward to seeing and hearing what the outcome is. dena


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RE: Making silicone molds...

Posted pics comparing straight out of the tube silicone caulk mold to a thinned with naphtha version. Check out trials and tribs in the link below. The pics aren't the best but the thinned version is definately better. Using the naphtha concerns me, even though I'm very careful. On another post someone recommended Xylol (Xylene)--any experience over here with that? Is it safer? Thanks,
Leigh

Here is a link that might be useful: Silicone comparison


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RE: Making silicone molds...

Hi,
I have a couple of plaster molds that I am also not wanting to break in the process of putting cement/concrete into. Here is a chart that might be helpful in answering some questions regarding mold releases. dena

Here is a link that might be useful: casting this into that


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RE: Making silicone molds...

Buddyfly,
How goes your molding experiments? your mask castings? Did you resolve the release agent issues yet?
Leigh


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RE: Making silicone molds...

Leigh, funny you should ask ... I left you a message in the "Vacation Tufa" thread. I guess you didn't see it. You can ignore that one now because I got through my crisis. I had to break the plaster mask (it was an inferior one that I used for a test run) in order to get it off. The nose broke a bit. I have 'my face' soaking in water now. Will post a pic soon. I'm wondering how to get all the vaseline residue off of the tufa face. Any tips? I read somewhere that rubbing alcohol works.

Re molds... I'm having more 'downs' than 'ups' I'm afraid. But that all comes when you have the experimenting bug, eh? I have broken a few plaster molds, torn a few silicone ones, MELDED a few silicone attempts with the subject that I wanted to make the mold of. Argh! Plus I have two cement stepping stones (my very first two) that are NOT HARDENING! And yes, I MEANT to yell that! So frustrated. What did I do wrong? I used a 1:3 portland/fine sand. Made a very 'toothpaste-ish' thickness and patted them into the molds. That was two nights ago and I can still press my finger into the cement! I am using the same portland bag that I have used for my tufa projects and it has worked fine for the tufa. All I can think that I did wrong was that I used sand from outside. I sifted it and sifted it until it was lovely fine stuff. Is it a 'no-no' to use sand from your yard?

Please help!

Buddyfly


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RE: Making silicone molds...

Buddyfly,
Sand from your yard shouldn't be a problem I would think as long as it's not contaminated with anything. What zone are you in? the reason I ask, is with the cooler nights here in wisconsin, I'm noticing some changes in curing too. There's a thread on another forum that's just starting to address the temp thing, link below. On the mask situation, did you by chance create an undercut by going to high on your forehead or to close to your ears? Just a thought to the issue of none removal. Someone did this with plaster gauze such as used on broken arms. Is that a little more flexable?
Leigh

Here is a link that might be useful: Temp changes & curing


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RE: Making silicone molds...

Leigh, thanks for that link. I applied to join that forum but will have to wait to be 'accepted'. In the meantime... what did you mean about the 'undercut' and using a plaster gauze?

I meant to mention that my nose broke because I hadn't carved the 'nostrils' flat. It created a barrier that the tufa couldn't release from. So I have made absolutely sure that the other mask of mine (the one I posted above) has the barriers removed so it should come off without a hitch.

Did you have any comment about what to remove vaseline with?

B.


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RE: Making silicone molds...

Hi Buddyfly,
Well this might sound weird but you could just use sand to cast a face. What I did was make a box with some "casting" sand (this is sand that is very fine and holds together well-it kind of actually locks) and then just held my breath and pushed my face in! I left the impression of my face in the sand. I then filled it with tufa. It works really well for tufa too because you can make your mixture a bit runnier-the water will drain out through the sand. Its in my yard now sticking up out of the ground. Looks cool.


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RE: Making silicone molds...

The nostril area is a good example of an undercut. On the inside of the plaster mold the holes are bumps which prevents the cured tufa from lifting out as it has formed around them. In your pics above, it doesn't look like the forehead or cheek area would be a problem. The lack of flexability of the plaster is probably the issue. I don't know how to remove the petroleum jelly. Does it leave an obvious layer or stain?


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RE: Making silicone molds...

Leigh, thanks for that undercut lesson! Appreciate that. I do think that was the problem on the 'not releasing'. Re vaseline... I want to try to incorporate this face into another tufa planter and I'm concerned that the tufa won't bind to the slight film that I still feel. I used a very soft scrub brush with dish soap and washed off the thicker layer of the vaseline but I still feel some oiliness. It might just be because it is still soaking wet. Tomorrow it comes out of the water bath and it will start drying out. I'll keep checking.

I experimented with carving my eyes open. Didn't work very well. The perlite caused problems... big chunks would come out as I was picking out the outline of the eyelids. It also is white (the perlite) and it looks weird with white spots on my eyes! With the next face I cast with my better mold, I'll skip the perlite and I'm also going to use a finer sand to assist with carving the eyes. In the meantime I'll pack on a little patching tufa on the eyes and re-carve them.

Will be posting that picture soon, I promise! lol

B.


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RE: Making silicone molds...

I decided to bump this post up before it fell off. It's got a wealth of information that it'd be a shame to lose.

Any of you cold weather folks make any molds this winter? Inquiring 'tufa minds wanna know...

peak


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RE: Making silicone molds...

Hi Peak...

Funnily enough, I just made a pile of silicone leaves yesterday!!! I had made a pile of plaster castings from the actual leaves in the fall and i accidentally broke some so i thought I had better get those silicone copies made! I'm going to be casting a few rhubarb leaves now. I have a lovely large catalpa leaf as well!

Take care!

Marly


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RE: Making silicone molds...

Hi
I am trying to picture exactly what you guys are doing...are you making the same type of molds that are being sold on ebay? they are blue in color (the ones that i have bought) and very flexible and slick feeling..they work great w/ clay, plaster of paris (if you coat the slilcone mold w/ vaseline or pam)..they are really exspensive on ebay if you want the real pretty ones..like the life like roses ...I bought a silicone mold of a rose trellis that is about 3 in high..and I just love it, but I paid 25 dollars for it..it works great w/ clay, doesnt stick and when the clay dries it comes out perfect...where can i get the materials to make those kind of molds? thanks in advance for any help,
Cherie

Here is a link that might be useful: silicone book in case soemone is interested


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RE: Making silicone molds...

peak


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RE: Making silicone molds...

Any Way to save this in FAQ?
Hate for this info to go away?


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RE: Making silicone molds...

such a wealth of info, I heard in one of these threads that 1 tsp vinegar per cup of water slows the POP set time, anyone have a firsthand info on that? sounds like a few of you could use that little trick

L


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RE: Making silicone molds...

Okay, I am having a problem. I had plasticine molding clay, and added a few shells, sprayed with Pam, and put silicone on the whole thing. Some kind of reaction is going on. I am having the plasticine melting? from the Pam? and the shells are leaching salt and forming crystals? oh my oh my what a mess. I have to leave it for another 24 hours, as the silicone is not entirely dry all the way thru, but I think it will be a disaster. Oh my. BB


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RE: Making silicone molds...

BB... is your plasticine "sulfur free"?? Sulphur will react to silicone and cause problems. Also, you don't need to use ANY release when you apply silicone to plasticine. It removes perfectly. I think the Pam may be liquifying the plasticine on you. When you added the shells, were they just imbedded or did you coat them with the plasticine? I was just wondering about that ... if they were not coated with the p. then I could understand that you tried the Pam as a release.

I feel so horrible for you with that mess on your hands. I had a disaster once with a tube of silicone that I think had been frozen in the warehouse at Home Depot. It NEVER cured and I had used it as a third layer onto two previously cured layers. It was just awful. I couldn't remove the guck because it was all gluey and it never cured! Eventually I scraped and scraped it off.

Chin up, you won't forget what you learn from all this!

Marly


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RE: Making silicone molds...

I arranged the shells on the plasticine and wanted to skip the POP. but should have use it first, then I would have had to recast in POP, then silicone to get what I wanted . I sprayed the shells with PAM and got it onto the clay as well. I won't know til tomorrow night what will happen, the silicone is thick in some areas, and not drying well at all. C'est la vie! BB


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RE: Making silicone molds...

Okay, I am really bummed out. This was a total, TOTAL failure. I made the face out of plasticine modeling clay, the kind they sell at the craft store or Walmart, etc. I had all these shells we had collected over the years at the beach. Okay, I made this face. I sprayed PAM onto the whole thing. Then put silicone directly onto the whole thing. Yeee gads. The silicone will not set up near the plasticine clay at all. the clay has dissolved because of the Pam? or silicone? The Pam may as well have been super glue as far as the shells go. It is one BIG GLOB of diddley squat. The shells do not come off at all. Whew, this is one for the garbage pail. I am going out to power wash my house to expend some of this pent up emotion and to do something other that cement/concrete/tufa/clay/shells. I need a break. On hiatus. BB

Here is a link that might be useful: bombshell, ha ha


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RE: Making silicone molds...

Oh BB I am so sorry that didn't work out for you... your project was absolutely stunning!!!! Just love the tree frog on the face!

I really suspect that the plasticine is at fault... if you wish to use silicone on it you have to buy that sulphur-free type I was mentioning in my previous post. I have a product called "J-Mac" clay. It was recommended to me by a gal on another forum. I bought it from a company in BC but the manufacturer is in the USA I believe.

Don't use PAM or oil on the sulphur-free plasticine by the way... not necessary and it will actually weaken the plasticine. The beauty of using plasticine is that it is re-usable! If you end up mixing in other elements like the PAM, it will change the chemistry in the clay.

When you come out from hiding from this project, why don't you try to make a mold of just ONE shell. That way you won't waste so much product on it, and you can play around with it until you find the right release agent. I would be tempted to try liquid car wax or vaseline. Once you have that part figured out, then the next step would be to get that proper plasticine.

Oh, and the marble for the eyes... on a face that I made a while back, I used marbles as well to ensure a proper round eyeball. I applied a very thin coating of the plasticine over it as the release agent.

I REALLY REALLY hope you try to remake this one... it is so beautiful!

Marly


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RE: Making silicone molds...

BB,

I acutally like what it has become....but then I'm strange like that...

Good Luck!


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RE: Making silicone molds...

grasshoppersilks, you haven't seen what it has become, that picture was before I added the silicone. what it has become is one pile of nothing. Absolutely nothing. I think if I had put POP on it, I would have been able to do what I started out to do. I put swirl shell parts for the eyes. I thought it would be nice to have that swirled iris. Oh well. I really got some cleaning up done outside, and still power washing the siding. It is a relief from frustration!! Wish I was closer to Baltimore. Lots of good art stores there. I have "real" clay, but would have to fire that after I made something to cast. I will go back to my leaf castings for a while. Much more successful!!!!!BB


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RE: Making silicone molds...

BB What a disaster and your project was fantastic - don't give up - do try to redo your idea, it really was great.

Jilly


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RE: Making silicone molds...

Thanks for all the morale support. I am still trying to figure some other way to do that shell face. Need new shells, as those are permanently imbedded in silicone. I'll let you know if I do it over!! BB


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RE: Making silicone molds...

That shell face was awesome. What a shame! I hope you got to salvage some of your shells, and I hope you try again.


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RE: Making silicone molds...

You could try sealing the plasticine clay before using silicone on it. The Smooth-on company recommends either acrylic spray or Supersealer when making silicon molds (but I've used shellac on plaster, no problem with silicon but very, very bad with polyurethane if you don't use a good release with it).

Here is a link that might be useful: making brush on molds, see step 2


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RE: Making silicone molds...

I think you guys are not using the proper "silicone" but the stuff in the tubes @ the hardware store. That stuff isn't designed for making molds. How can you stand to work with that horrible smell anyway? I think you would be much happier if you bought the correct products. Smooth-On sells many silicones, urethanes, resigns, release agents, etc. They are excellent products. They now have a new silicone product that is a trowlable silicone and slips off the model like a glove. I have bought some, but have not had a chance to try it yet. I have a gazing ball stand I want to make with it.
I don't mean to butt-in here, I just think you are wasting your time and hard earned money using the incorrect products.

Jan


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RE: Making silicone molds...

Jan,

"Correct" is what works. Not only does the caulking silicone work well for simple molds but it's a lot cheaper than Smooth-on and takes less time to dry.

Smooth-on is superior for complex molds but I think most of the folks here are making relatively straightforward molds of leaves and tiles and such.

peak


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RE: Making silicone molds...

Speaking of molds i've been playing around with different products to try to come up with a quick way of molding an object. The object of my "obsession" is a gothic naked woman handing on the bathroom door at my work. She is carved out of wood. I tried everyway possible to get her off from that door and couldn't. Latex took to many coats and it does shrink when hit with a hair dryer duh. Silicone, well i'd rather stick a nail in my eye before i'd use that smelly stuff again. So anyways, i ended up buying this product made from crayola called model magic. It is light weight, non smelling and very easy to work with. I sprayed some pam on her, slapped the mold magic over her, let it sit for a couple of hours and pulled it off. It picked up EVERY detail she had. After i got it home i built up the edges a little more, added some more details with the model magic, let it dry overnight and poured plaster of paris the next day. I finally have her. I'm sure i can tufa with this stuff, not sure how many casts i would get, but it worked great for this project. I bought it at hobby lobby, michaels also carries it. You can buy little packages of it or a tub with 4 packages in it for around 20 bucks. Hope this helps with someone elses obsession.


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RE: Making silicone molds...

Jan, I agree with Peak... we are mostly making straightforward simple molds. I use the caulking type because that is ALL that is available to me here in Pembroke. The cost of delivery of those better products would be prohibitive! I would think it would be cheaper if you buy the large gallon(s) containers of the Smooth-On products as well, and I don't think I would ever come close to using all that up for the shelf-life of the product. So I will stick (no pun intended) with my familiar caulking silicone. It works for me!

Marly


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RE: Making silicone molds...

Hey Julep let's see some pics!

Lee


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RE: Making silicone molds...

Buddyfly- I just finished reading this entire topic. Whew! Did you ever figure out how to make a mold from a real flower? I was wondering if you could freeze the flower to hold it's shape before molding it? May be a stupid suggestion, but I've yet to try mold-making.


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RE: Making silicone molds...

Actually MudMaker, I did end up with a mold of a Morning Glory!! I haven't figured out how I will use it yet because I figure it should be a very THIN casting and it will be a trick for me to accomplish that. I made that mold a LONG time ago and I am not sure how I made it... sorta forget. But I think I took photos of the process and I should look them up. I will post them in here in a new thread if I find them, OK? Thanks for the reminder to get on that! lol

Marly


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RE: Making silicone molds...

So glad this was bumped. There is so much good information here that a printed it out and have it in a binder. I bought some cheap "polyplast" clay from Hobby Lobby , made a model, painted it with Murphy's oil soap and mixed up 100 percent silicone from the hardware store, mixed that with a little bit of liquid glycerin and smoothed it dirrectly on the clay model.I put on several coats and it popped off of the clay very well. Thanks to all of the trial and error of these very gracious people on this forum. Thank yous gulys!!!


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RE: Making silicone molds...

I too have just read this entire topic - AND the Faux rock AND moulage - and I'm soooo glad it's been bumped up. What a treasurehouse of info you folks are! THANK you for such kind open sharing.

Um... at the risk of opening up a wound, that shell mask is so stunning - mass, delicacy, balance, lyrical line... I cannot help but mention that if you have any of those lovely pieces left sulking in a corner, there *are* solvents that will work on already cured silicone... solvents are funny things, verrrry specific and persnickety, but take a peek at the link below, won't you, ButterflyBush? Please?

(sheesh... yeah, yeah, I know... but see, what a strong effect a piece of original art can sometimes have on utter strangers, turns 'em into real pests...)

Kindest regards, either way.

; >

Here is a link that might be useful: solvent for cured silicone


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RE: Making silicone molds...

A golden oldie from page ten. This is much more popular during the winter months, when we're all driven inside.


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RE: Making silicone molds...

Great information for newbies and oldbies!


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RE: Making silicone molds...

I think this should be bumped too so here goes.


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RE: Making silicone molds...

Hi all, very new to all this and had a few questions. I have casted some leaves in concrete but would like to make a mold since i no longer can find any more huge leaves. Can i make a mold right from my concrete cast using silicone or will i have to use something else, if so, does the concrete need to be sealed first and also what release agent would i use , or do i need one,,Sorry so many questions but just want to make a mold so i can start casting leaves again. thanks


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RE: Making silicone molds...

ontariogal, I would love to also know if casting directly into concrete leaf works. Let me know if you tried this. Thanks for your time. Sher


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