Casting and Mouldmaking Instructions
Hydracast ART and CRIST
Hydracast ART is a ready-to-use material in powder form, for making Pate de Verre and casting moulds. It has a very fine grain and reproduces fine detail in the original. If using for 'lost-wax' casting you can de-wax with vapour using, for example, a wallpaper steamer. For glass weights 1-2 kg.
Hydracast CRIST has much the same characteristics as ART but is for heavier glass weights, from 2-60 kg.
Instructions for Use
Both products can be mixed either in free-air or under vacuum, as follows:
Mixing under Air:
The powder to water ratio is 1kg / 350cm3.
Ambient temperature should be 20oC or 68oF, if possible.
Always add the powder to the water, not the other-way-round. Gently sift the powder into the water between the fingers from above, allowing the water to absorb all of the weighed powder before starting to mix.
Once all the powder is introduced to the water, and wearing a pair of rubber gloves, slowly begin to mix the Hydracast and water together. Spread your hand under the surface and gently agitate from side-to-side being careful not to introduce air into the mixture. Mix in this way for about 6 minutes, no longer as the mixture will begin to set.
Once mixed pour the liquid slowly into the mould container, down the side of the mould-positive, being careful not to introduce any air into the mixture. Leave the mould for approximately 20 minutes until set. Setting time is shorter in Summer (10-15 minutes) and longer in Winter (17-22 minutes).
Mixing under Vacuum:
The mixing time will be 5 to 6 minutes with a powder to water ratio of 1kg / 340 cm3 (1kg / 330 cm3 in Winter).
Drying of Moulds:
Allow the mould to airdry for between 6-24 hours before attempting to remove the positive material.
Fondu Cement and Vermiculite Mould-mix
For durable slumping moulds with no undercuts.
Prepare the original model and coat with Vaseline, grease etc The ratio of Fondu Cement to Vermiculite is 1 to 3 (or 4) parts. You will need sufficient water to create a paste.
Mix the dry Vermiculite and Fondu Cement evenly. Mix small amounts separately with a whisk and keep in a separate container covered with a lid.
Prepare only sufficient to be used within the next 2-3 days. Fondu Cement absorbs humidity from the air which may lead to premature curing.
When mixing with water, mix a small amount of cement (appoximately 2 litres) with about 0.5 litre of water. Mix by hand. The mixture should be of a firm consistency, not too dry and should not break apart (similar to a snowball). If necessary add a little water (too much water will weaken the mould).
Continue until you have prepared enough mould-mix.
The Working Time is a maximum of 1 hour. Make sure the model and mould-mix, plus accessory materials, are prepared and ready.
Build up the mould-mix to a thickness of 1 - 1.5 cm. The first layer of the mix can be slightly wetter. Then build up to approximately 2.5 cm.
If necessary use reinforcement materials.
Build up to a further 5 cm thick. The mould thickness should be uniform as this helps with the cooling of the glass.
Hardening and Drying
Wrap the mould (with the model) in a plastic sheet or plastic bag and close tightly. Let the mould harden for several hours.
The drying process should start after the mould-mix is fully hardened. Caution: Mould heats up during curing.
If you make a multi-part mould, because you have undercuts, you can build a new mould element on top of a fully hardened part.
When the mould is fully cured, airdry or use a fan.
For chemical drying fire the mould to a temperature of 540oC. Important: Heat up the mould SLOWLY.
Once dry, coat the mould with Shelf Primer, such as Bullseye Shelf Primer.