I don't do papercrete but if you want to get better, cleaner colors use white cement not the more common grey.
Regarding the lime, I use a water bath for my hypertufa. I unmold in 24 hours and put in a water bath for 3 days, changing the water each day and plant. A long time ago on this forum, we had a debate about the lime in the planter. There are very few plants that are lime sensitive and some people felt that the soil buffered the plant from the lime and as you water it rinses out the lime. I've never had a plant die but worry that someone can get a burn from the lime if they handle a fresh planter, so I use the water bath.

Thanks billie_ann for your input, it makes sense, about both of my problems.

Awesome look! Where do you get oxide powder? What's the difference between papercrete and hypertufa? Googling now. :)

i am using Iron oxides from ceramics supply houses. umbers,raw, burnt and so on are primarily iron there is also red, black, and yellow available from www.lagunaclay.com. Green is copper or can be chrome. i am staying away from these because these elements can be unhealthy. blue pigments are in general synthetic or cobalt another potentially toxic ingredient. For achieving blue and green use ceramic tile.
One can mix one part iron oxide to eight parts Portland cement, use this as a paint in the form. For glossy finish i like to use plastic bags or similar sheet plastic to line forms and paint into the forms then place the cement material. In the case of tile or bits of glass we can make clay forms that hold the tile bits also we can glue with rubber cement the tiles in place. Still this is nothing specific about papercrete.

I'm looking for a lightweight material to make some rather large planters. I thought hypertufa was the way to go but was told hypertufa is not intended to be lightweight. Would papercrete planters be lighter weight than hypertufa?

Papercrete is something I missed for long time but now when I started to make it I cannot stop! I always need pots for my plants but my fuchsias do not like plastic (I don't like it also) and terracotta is too heavy and too expensive. So my idea was to make something that is lightweight, looks natural and will protect the roots of my plants.
Here are my first trials (hope pictures will appear)
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The square one is still to be finished. I made my planters waterproof so mould doesn't grow on them.

Very Nice Martin. I love the texture. I take it you have put drainage holes in the bottom?