Materials Lesson in the Sculpture Room
Demonstrator: Steve Hans
The sculpture class this year has branched out into areas that I hadn’t even thought about before. We are experimenting with materials I haven’t touched for many years, or have no experience with at all.
I am not planning on taking my career in the specific direction of sculpting, but I have dabbled in the recent past mostly for my own enjoyment and it doesn’t hurt to not only get outside your comfort zone a bit, but also know that you have skills just in case you need them.
We had a visit from Steve, who has many years training and experience with various moulding and casting materials for artists. He demonstrated and explained a lot of materials that we had little exposure to and had not seen in class yet.
First he told us who the suppliers are in case we need to contact them. In Australia they are Gel Chem, Barnes and Solid Solutions.
Steve gave a demonstration of Dental Alga by casting a student’s hand in it. It was later filled with a solid casting material and allowed to set. Dental Alga is safe to use and breaks apart easily so the whole process isn’t too frustrating.
We were told about rigid and flexible moulds. Rigid moulds do not bend and flexible ones can be made of such materials as silicon or rubber and they can allow for undercut to prevent breakage as you pull your piece out of the mould.
There are also single or multi part moulds. The single part moulds (plaque mould) can be silicon and are usually one sided. The multi part moulds use what is called locators so that the parts can be made to line up with each other, a pouring sprew (an access hole for pouring in material) and holes for air to escape to prevent bubbles and air pockets)
Moulds can allow for multiple of original sculptures, they can be made of plaster bandage as well which has cut lines included so they can be pulled apart when set. These are useful when casting body parts.
We had a practical demonstration of how to create a flexible mould in Dental Alginate. It was interesting that it had to be done very quickly as the material sets fast after mixing.
We also saw how the Hydrastone was mixed to go into the hand cast. This material is based on gypsum and comes in a powder which is mixed with water and is very strong once set. It is up to five times stronger than normal plaster.
We learned that a mould that is cast and then smashed off the casting is called a Waste Mould.
We learned that a Ceramic Cavity is the name for casting things such as plates and other crockery and it is also called Slip Casting.
We were reminded that the best way to dry plaster is in the fresh air and not to try to speed up the process with a heater for example, as it will only make it crack.
We were given a demonstration of paint on latex and it was explained how time consuming the application is, requiring many coats to be painted on and drying time between each one. It was also explained that this material is very flexible and only has certain uses.
Steve had examples of how to make up the base, frame etc for a silicon mould and had brought along several previously created versions. He even gave us pricing on materials and drew up diagrams so that it was easy to see the methods and why they were necessary. The need for scales and accurate measuring was emphasised as if your quantities are wrong it will effect setting time or stop the material from setting at all. We were also told about the health risks for materials that were a bit more hazardous.
For much of the casting we were told to keep plenty of paper towel handy as keeping the work area clean is very important. Some of the materials set so fast that having an extra person to help is also very important.
We were told about the difference between Condensation Based and Platinum Based casting materials. Apart from the cost. They are:
Tin Based: Shrinkage is 1-5% so can shrink from 10-50mm per metre of cast, cures over most bases, shorter mould life, if you use more cat list you get a faster cure, less and you get a slower cure, approx. $50 per kilo
Platinum Based: Shrinkage of less than .5% which is less than 1mm per metre of cast, affected by substrate especially won’t cast over rubber, latex, epoxy, shellac and some paints, longer life mould, cure faster in heat and slower in cold, approx. $70 per kilo
We were shown examples of objects in resin. Many objects can be preserved for display using this method. (even leaves) We had a practical demonstration of how to mix and pour the resin. It was pointed out that there is a lot of work done after the resin is pulled out of the cast. To get a professional finish cutting and polishing is involved.
Other materials covered were Polyurethane which can take special colours to make the casts more exciting to look at. Clean Clay which is good for modelling as it isn’t as dry as most other clays once set, Scalpie which can be dried in an oven and is good for modelling and sculpting and a “Wound Kit” which anyone who likes special effects would love as it creates the most horrible looking special effects wounds for the human body.
The session was quite intense with information and went overtime but Steve was very informative and entertaining so I enjoyed the lesson and demonstration very much. I have more detailed notes in my journal for future reference including diagrams, so if I need the information it’s there ready to go.