I have been using Sculptamold (over plaster cloth or foam, etc) to form my scenery base. The problem I am having is that a mixed batch of Sculptamold starts to set in the mixing bowl very quickly, making it much less workable - 5-10 minutes is the most I can get. And if I make a second batch in the same container, this goes off even quicker, unless I wash out the bowl each time (and there is a limit on how much sculptamold I can pour down my home drains without clogging them up). As I am trying to mold my scenery as I go, this isn't enough time unless I make very small batches. Is there any way to extend the working time of a batch, so that I can mix a reasonable amount at a time?
Welcome to the world of cementicious materials. Like any material of that type it works on exothermic reaction and heat Input. Warm water, hot water makes it go off faster. So does an warm room. Only solution, since you can't get plasticizers and such. Is ice water. That slows the process. Making the material have to warm up first before the chemicle reaction can start. Same process for concrete in the summer. Bring the temp down. It will work with hydro cal And plaster too since they are also cementicous materials.
shane
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Huh, that's interesting. Sculptamold is usually known for having a relatively long working time. No idea why it would set up so fast.
Use a flexible plastic container for mixing. Then let it set and flex the bowl to pop out the hardened pieces. Don't put it down the drain!
I use Gypsolite. It seems to have plenty of working time, and I like the gritty texture for scenery. I coat it with washes of green and brown art paint in a camouflage pattern. After that dries, it gets ground foam, turf and/or static grass.
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Having worked with Sculptamold quite a bit, it almost sounds like you might be making the mixture too thick. (e.g. not enough water to too much mix) Sculptamold is one of the few modeling materials that you don't have to be exact with on the mixture in my experience. (I tried Hydrocal once and hated it.) I have found that a mix of about 1.5 parts cold/cool (usually room temp) water to 1 part Sculptamold seems to work very well for me. For some things that might be a bit wet but it extends the work time. I don't use it to mold. I usually spoon it on to my foam base and use the back of the spoon to smooth it as needed. By using the spoon from the bowl I can get the excess water out.
Another thing is to mix it until the Sculptamold is just moistened. (Don't overmix it.) Think of it as making a cake. (Yes I know some of us modelers are not bakers but the idea it the same.)
I have also found that Sculptamold doesn't seem to heat up (exothermic) when it sets. Anytime I have placed it on foam, it always remains cool to cold (endothermic) when I have checked on it even two hours later. Of course, I could always be doing something in error.
I will just repeat what has already been said, use cold water and add more water, I too think you may be making the mixture too dry or firm. Perhaps make up a bit less at a time and have everything ready to go once you have it mixed up.
I use a big inexpensive bucket of plaster joint compound. I believe it has glue in it the makes it bond with underlying material. I spread it over styrofoam or wood. It takes a couple of hours to harden beyond sculptability. It takes a day to fully cure. It is the right consistency in the bucket, so I don't have to add water. I sometimes add dry pigements.
Don't put plaster down the drain. I take any containr and tools outside and rince with a garden hose. The big bucket is resealable, so I just put the lid back on and save the rest for another day. A well sealed bucket will last a year.
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Thanks for all those thoughts. I will try making a slightly thinner mix next time - as long as it's not so thin that it runs away, it might be OK. I have found that adding more water once it starts to harden will sometimes delay the inevitable, but I can only do that once or twice in a batch.
I wondered about using drywall mud, but am concerned that thicker spots (which you are going to get in places) might crack too easily - even when drying out. But it would set much more quickly than sculptamold (which typically takes 2 or 3 days to become sandable), and I'm sure that it's cheaper.
I generally mix the Gypsolite as almost a slurry, very thin. It still goes on and holds its shape very well. Out of the bottle, it's gray, which is acceptable for granite. I might squirt in cheap artist acrylic of green or brown to get a different natural look, but I don’t worry because it takes either thin or full-strength paint very well.
Why not use Plaster of Paris?
Over plaster cloth just use plaster of paris but if you used the plaster cloth right it should rairly need a covering. To use plaster cloth corectly, dip it and apply it with the side with the most plaster up (yes there is a difference but it is less noticable in the better quality stuff). Next you need to smooth it, I ussually use my bare hands, that will fill in most of the holes. If you are going to zip texture the first layer of scenery, don't let the plaster cloth dry too long to get a good bonding.