Sealant for Slip Cast Molds
When mixing mold soap use a 1:1 ratio of the concentrated gell-like soap (Axner/Laguna’s) to water. So you can mix a container ½ full of soap concentrate and then add the other half of water. Use warm water, stir well and let the solution dissolve for a couple of hours.
Do not use Vaseline as a resist for plaster to plaster on a slip mold… it seals the mold and it will not absorb the water from the slip
1. After the first section is cast clean the plaster surface and cut the keys.
2. Add liquid slip to the perimeter of the model to be sure the model is completely sealed along the seam line. Sponge off the excess and look at the seam between the plaster and the model for tiny opening and air holes. Leave what remains there to seal the model tight so that you have no plaster leakage when you cast the second piece of the mold.
3. Add three coats of liquid mold soap. The first coat is the most important for it will fill the pores of the plaster. Brush the soap on generously and wipe dry with a soft brush. Add a second coat and then a third in the same manner.
4. You are ready to cast the second section. Attach you coddle boards. Add clay coils to seam lines. Weight plaster and water ratio. Mix and pour.
Sealant and resist for plaster press-molds:
Smooth-on super seal sprayed as per product instructions. Three coasts of mold soap, let dry between coats then buff with a soft cloth.
Measuring Volumes for plaster
Measure the L x W x H within coddle boards and then subtract the estimated space displaced by the model and this will give the Quarts of Water. Then match this number with the plaster ratios listed on the chart.
You now have the amount of water in ounces and the amount of plaster in pounds.
454 gms. = 1 pound
28 gms. = 1 ounce
Websites:
Fractions to Decimals – www.med.wayne.edu/biomedcom/fraction.htm
Quarts to Ounces – www.asknumbers.com/QuartsToOuncesConversion.aspx
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