May 21, 2008: burnout and Casting in Colonial Williamsburg

George Cloyed

Giles Todd

Tonny Beentjes

Pamela Smith

BURNOUT: May 20 by 5pm: All molds in the kilns.

3 crayfish molds in the kilns at up to 600 deg C = 1120 F for 3 to 4 hours

6 plant and grasshopper mold up to 500 deg C = 950 F for 2-3 hours.

Into the kiln at 5pm, up to temp at 7:15, turned off at 9:45 and left to cool in the kiln. [George would take about 5-8 hours to bring it up to temperature. HEAT MOLDS MORE SLOWLY.]

Notes:

Ms: bismuth only added to tin and lead

Kunckel: bismuth added to silver and to tin and lead

Sal ammoniac not really added to any metals, although it “cleans” a lot of them

CASTING

I: Juniper (2:1 plaster to brick) 8:1 tin to lead mix with a bean of bismuth

This one came out very sharply, although the mold cracked from the inside—perhaps the bismuth expands?

Metal was glowing red-hot; Tonny has never seen it so hot

II. Yarrow: (2:1: ½ talc) 8:1 tin to lead mix w/ a bean of bismuth

Very sharp, but soft and malleable.

Heated molds up and then let them cool to put finger in gate and doesn’t burn the finger

sal ammoniac added to all silver; molds heated red hot

III Yarrow: (2:1: ½ sno white filler) w/ sterling silver

Metal did not fill all parts of mold. The leaves just sticks, but mold did not crack at all; seems to have been strong

Silver was very hot—very fluid

V Yarrow: (3 parts plaster and sno-white filler (in equal parts) and 1 pt brick) sterling silver

Metal did not fill all parts of the mold. Mold cracked from within (so couldn’t be bismuth).

VI Pansies (2:1: ½ feldspar): sterling silver

Tremendous detail—worked beautifully

Crayfish:

  1. in 1 lb lead to 4 oz tin

    1. not as sharp as the tin and seems like it’s corroding fast (?)—darker and not as sharp two days later, or so it seems

    2. lead was red hot—too hot; it oxidized

The following two crayfish molds were poured in the press.

  1. 1 lb tin to 2 oz lead - no bismuth – not as sharp as third crayfish

  2. 1 lb tin to 2 oz lead, bismuth – very sharp, shiny and excellent

Grasshopper mold fell apart- probably heated too much (put on top of coals before casting)

After casting, we put silver molds almost immediately into water and this allowed us to get the objects out much more easily.

We let tin/lead molds air cool before putting into water—the metal stays liquid longer and so if you put it directly into water, it would explode. This allowed us to get the objects out fairly easily.

I think we need to heat the molds less—the heating seems to make them too fragile, and they are really well burned out.

George Cloyed observations: Wire and lute molds. This important.

Heat silver molds hotter than they were heated this time.

Tin molds--don’t heat them quite so hot. Pour metal, especially lead, at a lower temperature. Just melt the lead then pour it quickly. It heated too hot and was vaporized today.

Redder molds (more iron oxide? More brick?) came away better from the objects.

Tin mixtures worked better than lead mixtures.

George thinks the ms. could be a workshop doc because learning necessitates writing down. Master may show an apprentice something and then he doesn’t do it again for a long time…has to remember this. He showed me Lynn’s notes that she keeps in the workshop.

Tonny observations: success w/ heating the molds is important. Make sides of mold flat.

Press worked better—made less flashing