Casting

[Laurence Finston]

I decided to go ahead and try casting the papier-mâché without touching up the molds. They're still giving off moisture, so I don't know how long it will take for the paper to dry. I expect that the plaster will absorb the water from the paper even so, but I'm not sure. However, nothing terrible can happen and if it doesn't work, I'll just scrape the paper out.

There are a couple of fairly big holes in the negative "casserole" mold. I'll fix them with spackle. This will wait until the papier-mâché either dries or I take it out.

I'm trying to make "caps" or depressions using the positive molds. On both kinds, I've put in a generous amount of papier-mâché because it will shrink as it dries. However, unlike plaster, it should work to add new papier-mâché to some that's partially dried.

Plaster, on the other hand, has the unusual property that it expands as it dries (and hardens). This is much better than shrinking.

I left a lot of papier-mâché around the hole or the bump as a margin, but I didn't bother to put up a "fence" to contain it. If it works, I'll just trim it when it's dry.

I didn't coat the molds with vaseline because it would be impossible to get it off the paper and wouldn't make for a nice surface. In addition, since the paper will shrink, I'm hoping it will just pop out of the mold.

An alternative would be to rub tincture of green soap into the mold, which doesn't leave visible traces on the surface. I even have some of this. However, I should sand the molds first before doing this. If I don't have to, I won't.

[Dave Pete]

Give some thought to making your molds by recycling the plastic heat formed containers many packaged goods and foods come in. Heat the plastic then push the dapper into the warm plastic. I'll bet with a little practice you can make pretty decent molds.

[Laurence Finston]

Thanks for the suggestion. I'd like to know what they're made of before doing this, though, and what fumes heating them would release. On the other hand, I'm all for recycling, so if it can be done safely, it would be worth a try.

One thing I like about plaster, clay, (rag) paper, shellac and linoleum is that they are natural materials or made of natural materials and non-toxic. This applies to beeswax, too, but I save my beeswax for encaustic painting. The beeswax I bought for this purpose recently is refined and has virtually no odor but I have some for candles that had been in my basement since 1999 and still smells absolutely wonderful; even some that wasn't even wrapped up. However, it would be wasteful to use something fine like beeswax for this purpose when paraffin will do. I don't know whether paraffin is non-toxic or not. Wax fumes certainly aren't healthy, probably not even from beeswax.

Other materials used for molds are casting sand, silicon and latex, but I've never tried them. They're available at hobby stores. I bought some latex once but never used it and it hardened.

[Laurence Finston]

The papier-mâché is definitely drying, which is a relief. Nothing to see, so no photos.

Papier-mâché is tough and elastic, so I'm hopeful that I can pry it out and off of the molds, respectively. Otherwise, I will saw through them to make two-piece molds. I'll have to buy a new saw blade for this, because I don't want to ruin my good ones.

I figure I'll have to wait at least until this evening if not longer before trying to get the papier-mâché out, but I think by tomorrow morning at the latest it should be dry enough.

[Laurence Finston]

The clay is too soft and sticky, but I've pre-formed a hole and will leave the container open and let the clay dry a little on the air. I've put some on the drying slab, too. What I want is a leathery texture. I'll have to watch this, because it's likely to go fast and the process is not reversible. Connected with this is the fact that you can't reconstitute partially-dried clay; you have to let it dry completely, break and/or crumble it up and then put it in to soak.

Since the papier-mâché started to dry, you can practically watch it happening. I'm trying to keep myself from worrying at it. I think it should be ready to take out in a couple of hours. The paper is sinking into the holes of the negative molds, so if I wasn't in a hurry to see whether it worked, I would fill them in with more paper. That's what I meant when i said that it was better that plaster expanded. However, I can do this later, either (probably) putting the domes back in the molds or leaving them outside.

The difficult part was making the first positive and negative molds. Now that I've got them, I can reproduce them as many times as I want pretty easily and it looks like casting in papier-mâché will work so I can make as many domes and caps as I want. I hope I'm not getting too optimistic.

[Laurence Finston]

Originally Posted by Laurence Finston

I didn't coat the molds with vaseline because it would be impossible to get it off the paper and wouldn't make for a nice surface. In addition, since the paper will shrink, I'm hoping it will just pop out of the mold.

An alternative would be to rub tincture of green soap into the mold, which doesn't leave visible traces on the surface. I even have some of this. However, I should sand the molds first before doing this. If I don't have to, I won't.

It occurred to me later that it doesn't make sense to use vaseline, green soap or anything else in this case, since I want the plaster to absorb the moisture from the papier-mâché.

The paper is nearly dry but not quite, so I will check on it tomorrow morning.

[Laurence Finston]

I've taken out the first dome and cap. The others are still drying. The dome was a little lopsided, so I touched it up a bit with some fresh papier-mâché.

When I made the holes with the punches, I failed to account for the thickness of the casting material surrounding the dome, so I tried to make the hole as close to a hemisphere as possible. With this mold, I pressed the punch in deeper.

The second casting is just a block using the excess mixed plaster. I can use it for my lettering project.

I'll let the mold dry and harden overnight before casting the negative.

The hole got distorted when I removed the cast plaster mold. from the container. It doesn't matter. I sprayed the clay with water and it can be used again until it gets too dry.

[Laurence Finston]

The papier-mâche is still partially wet, so I've decided to leave it alone for awhile.

Space is at a premium in my kitchen, so I started stacking the cooling racks with the drying clay and plaster.

The wax that gets into the water in the party pan cools and forms a layer on top of the water. It is easily removed. It looks substantial, but it is so thin that it melts down to nearly nothing. When the wax hardens, you can pour off any remaining water, bits of clay and plaster, dust, etc.

Years ago, when I was working with paraffin, I stored it in glass jars. I had a lot of these in my basement, but I'm gradually working through them. This isn't a good way of storing wax, because the glass will eventually shatter from the heat. I now use metal and ceramic objects for this purpose.

I'm using wax to surround the mold this time. It took a little longer than expected but it makes it easy to separate the mold and the cast and clean up is much easier than with clay. I will take a break before touching up the wax with the hot air gun and modelling tools. Then I can pour the cast for the negative mold.

[Laurence Finston]

Cast the negative mold. I'll give in an hour or so while I do some other things and open it later.

[Laurence Finston]

It took a little longer to separate the mold and the cast than it would have with clay, but cleaning up is easier and you don't have to wash the cast or the mold. Wax is even better than grease for protecting tools, so you don't have to make sure you clean them up right away and get off every speck.

I finally ran out of patience and tried to get the rest of the papier-mâché casts out. Two depressions turned out pretty well. I destroyed one getting it off. It had stuck to the plaster, which had probably still been too wet. One dome turned out pretty well, another one too, except that it will require some surgery. The third one isn't dry yet so I will leave it in the mold until it's thoroughly dried.

Next time, I'll try using wax for the impression from the punch again. I think it might be possible to get better results than with clay after all.

I'm pretty sure I can get better results by using molds like the new ones, where I pressed the punch in further. Also, by waiting for the molds to dry completely before trying to cast anything and leaving the papier-mâché alone while it's drying.

All in all, I'd call my first attempt a qualified success and pretty good for a prototype. By the time the new molds are dry, I'm sure I'll feel like working on this again but right now I'm looking forward to doing something else.