Experiment 2009 Amsterdam Crayfish molding
June 24, 2009:
P. molded 1 crayfish, pressed back into clay
Plaster poured in two goes (wetter plaster mix separated from more solid one—had to patch w/ another layer of plaster, which separated in the burnout)
2 x plaster of paris
1 x chamotte
2 TBS iron oxide
Sal ammoniac 2 tsp mixed with water and 1 egg
Dried in hood for 3 days; put in kiln: 1 hour up to 60 C, then ½ an hour up to 80 C for 3 hours
SEE below
T mold
Build up method
2 x plaster
1 x chamotte
2 TBS iron oxide
Sal ammoniac 2 tsp mixed with water and 1 egg
Dried in hood for 3 days; put in kiln: 1 hour up to 60 C, then ½ an hour up to 80 C for 3 hours
SEE below
P. mold
Build up method
2 parts plaster
1 part brick
½ part talc
2 tbs iron oxide
Sal ammoniac, water, egg
Dried in hood for 3 days; put in kiln: 1 hour up to 60 C, then ½ an hour up to 80 C for 3 hours
29 June: at 4pm, all molds put at 98 C until 9am on 30 June, then heated up to 500 in 12 hours, then at 500 for 3 hrs, then cool down so we can open up, clean out, wire back up and lute w/ plaster [note that we decided to do ½ plaster, ½ filler –part bricks and part baked plaster molds as the ms. says to do, but the kiln baking the plaster shorted out and we will do it overnight? Did not do this.]
1 July: at 8am, the kiln was at 230 C, so had to wait to take out molds. They began to be cool enough at 12:30pm, but I went to Rijksmuseum with Muki and Zori until 3, then went back and had a FRANTIC 3 hours
cleaning out the molds
rasping them off to make them flat
putting metal plates on them and wiring them closed (I do not know how to twist a wire with pliers to tighten it, but, actually, what I did was just fine in the casting, and then the next day, I got a lot of practice and better at it.)
putting a 60/40 (plaster/grog) mix on the seams—I made a very messy and rushed job of it.
putting them back in the kiln
getting out of the building by 6pm
CRAYFISH molds after burnout:
Tonny’s was beautifully clean and well positioned; impression of crayfish back shell was particularly sharp. It cleaned up very nicely—I got virtually all of the crust out.
Note KEYSTONES at the back in order to fit the two halves together again
FLAT sides helped a lot in fitting the clamp
My molds:
Crayfish 1:
Non-build up method—very good impression; opened well, but did not try to clean everything out—want to see what happens (didn’t make much difference to the cast—it fell away easily from the metal cast and left a nice impression—although some black bits).
Crayfish 2:
This was the messy one that fell apart and came loose from the wax runners and vents, etc, but the impression and positioning actually looked good. Did not try to get all crust out.
ALL MOLDS WERE VERY SOFT AND FAIRLY CRUMBLY, BUT THEY WORKED FINE IN CASTING AND TAKING OFF THE METAL—THEY CAME AWAY EASILY AFTER BEING SOAKED IN WATER—more easily than some previous molds.
I HAVE NO IDEA WHETHER I MADE THE WIRE TIGHT ENOUGH- yes!- AND WHETHER THE LUTING WILL DO ANYTHING—IT WAS WATERY AND FULL OF GRAINS. Yes! I WAITED FOR IT TO SET SLIGHTLY BEFORE GLOPPING IT ONTO THE SEAMS. Not necessary—could have worked even better to pour it on liquid so it entered into the opening betw the two halves.
2 July: casting of pewter into crayfish molds worked well—no cracks, burst molds, etc., but the molds seem to have been too hot, as the detail on large surfaces was not good, but the quality of narrow tiny claws on feet and the back feathery legs was stunning.
The mold was probably somewhat too hot, as the surface of this and the crayfish was not sharp and kind of opaque. (I think the pewter doesn’t cast as well as lead/tin mixture.)
USE A WOODEN SATAY STICK OR SIMILAR TO CLEAN OFF MOLD MATERIAL SO YOU DON’T DAMAGE THE METAL CASTING
CASTING PEWTER
Muki took movies of this.
Nb: density of metal on stirring. When it begins to show ripples on any movement, it’s liquid enough.
Soaking the mold—be careful trying to open because the tin may still be in a slushy state.
Tonny’s mold sat over the weekend and he took apart by hammering with a mallet, but it broke off some delicate part.
Finishing
July 6: cut off all flashing and channels, runners, with a piercing saw (and many sawblades!) and just tearing off the flashing by twisting with pliers and fingers.
Cleaned up crayfish in about 2 hours/crayfish (taking Jonah to Rijksmuseum in between).