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some tuf questions
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Posted by moksha SA Aust (My Page) on Fri, Oct 30, 09 at 21:51
| Hi, I'm interested in trying to make a couple of large round hypertufa pots using a plastic basin - I guess they'd turn out to be 1 to 1 1/2 ft. wide.
1) Would I need fibreglass reinforcement?
2) I've got COARSE grade perlite. Is this too big? Would something like vermiculite be better?
3) Is turning out a pot OK, as I won't be able to pull the sides away obviously.
Thanks in advance. |
Follow-Up Postings:
RE: some tuf questions
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Just want to be sure you're talking "one foot" measurement.
If that's the widest part, you won't need reinforcement unless you are making very thin walls. Wall thickness for that size should be 1 1/2 to 2 inches thick. I've made a 4 foot long trough with no reinforcement but the walls were 2 and 1/2 inches thick.
The coarse perlite can be a problem. If it's too large and it settles on the outside of the pot when you're making it; it can leave too many voids. Large pieces of perlite have a tendency to wash out on the outside of pots. I think that someone on this forum chopped their perlite up.
I use large plastic bowls and tubs but they can't have any undercuts. The undercuts will grab and hold the cement mix and you'll have to cut it off. If the plastic pot has a design that you want to use, you cut the pot almost in half. If the mold is a flexible plastic, cut straight down both sides to the bottom but leave the bottom intact. If it's a rigid plastic, cut the bowl completely in half. Use duct tape to hold the sides together when using the mold. Use lots of duct tape and go all the way around the container. Make sure you spray/coat the plastic mold with a baking spray, vegetable oil, vaseline for a release. You only need a thin coating. When you use plastic molds for the first few times the cement mix will come out without using a release but the lime in the cement etches the plastic and after a while the cement mix gets harder to get out. Just using a little release will save your molds for a long time.
Unmold in 24 hours and before you do anything else, wash out the molds right away with a little soap and water. Even leaving a little cement mix to harden will wreck your mold. Then go back to your pot and clean it or wash it. Wrap in a plastic bag and leave in the shade for a couple of days. Or if you have a large enough bucket put the pot into a water bath for a few days.
Hope you have a great time and let us know how you made out. Billie |
RE: some tuf questions
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| Thanks, I thought the perlite might be a problem as it rises in potting mixes too. Cutting it up would be a hassle so I might think about getting some vermiculite. It's just a normal plastic tub with handles, I don't want to cut it but I was thinking of lining it with plastic. I guess foodwrap would work? I have no inner mould, I was just going to do it by hand and work the mix up the sides using a stick for a depth gauge. I have a couple of Aloe Polyfilla's that need repotting and I can't find anything suitable. I need width rather than height. |
RE: some tuf questions
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Lining with a plastic bag (dry cleaning bags are great) or spraying with a release is the same thing except the plastic bags will leave wrinkle lines and sometimes get embedded in the cement mix. That's why I usually op'd for a spray release, it leaves a smoother, clean looking surface. I do a lot of leaf imprints on the outside so I don't want the "wrinkled" look.
You don't need an inner mold. I make "hamburger" patties going up the sides of the mold. Make a patty, slap it on, place another patty along side, going all the way around in one layer, patting, blending and smoothing as you go. Then move on to the next layer of patties. Good luck! Billie |
RE: some tuf questions
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| 1st attempt, now at about 20hrs old. Coir, small perlite & light colored cement were used in roughly 1/3 ratios. I'm pretty happy with it but the bottom is a little thicker than I would have liked and it's a little heavier than I thought. Wire-brushing really brought it to life. I want to drill some holes in the bottom. Should I do that now? 
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RE: some tuf questions
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| Ahh well did it & it was fine. Did some heavier filing, washed it down and bagged it. It looks really great, Mum's getting it for Christmas! :) How do colored pigments look? I was going to go for some terracotta. |
RE: some tuf questions
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| Nice job. What did you use to put the groves in it? I haven't tried the wire brush. Nice to see the results you got with it. Kathy |
RE: some tuf questions
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| Metal files. Don't know why I used them as there were some pretty abrasive wood ones but even at 18hrs old it was still pretty tough going. Trying to do anything more elaborate would have been impossible - it was straight lines or nothing. I guess putting in less cement may be helpful. I just grabbed some masking type & stuck it round as a guide as I had no string handy. |
RE: some tuf questions
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| Final product - I just love the way this stuff looks, the texture. The perlite is awesome. 
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RE: some tuf questions
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Looks great!
What are the fuzzies? Did you use fibreglas reinforcement or is it from the coir? If you didn't already, you can use a butane torch to burn off the fuzz.
The picture above where you say it's 20 hours out....the piece looks older than 20 hours. Usually I unmold in 24 hours and it's still a dark wet-looking grey and the piece is easy to work with a wire brush or carving tools. Usually after 48 hours the piece is hard as a rock and hard to carve without power tools.
Watch using pigments, stains or dyes, if you add to much your piece won't cure and some colors if you don't add enough you get some horrendous colors. One of my earlier pots, using terracote cement dye, came out the ugliest pink I've ever seen.
Your pot does look wonderful and I'm sure your Mom will love it. Billie |
RE: some tuf questions
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| Thanks Billie & thanks for your help too. The odd strand you see is only coir and it was only 20 hours old in that photo, actually more like 18. It was already set solid, I was surprised myself. |
RE: some tuf questions
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| I don't use coir. Wonder if it sucked the moisture out of your piece. Or is it very warm in your climate and the piece got baked? It shouldn't be set solid in that time. Did you mist and store in a plastic bag out of the sun for the first 24 hours? Billie |
RE: some tuf questions
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