Monday, June 14, 2010

Preparing Slump and Drape Molds

When it comes to shaping glass in a Paint Your Own Pottery studio you have two options, slumping and draping. Slumping is done in a bisque mold and draping is done over a stainless steel mold. Why are there two different materials? Let me explain. Bisque, stainless steel, and glass all expand and contract at different rates. Bisque expands and contracts slower than glass, and stainless steel expands and contracts faster. So, what does that mean? It means that you want to slump glass inside of bisque, and drape glass outside of stainless steel. Clear as mud? Great! Now that we have that out of the way, lets focus on preparing molds for shaping glass. Molds need to be primed prior to firing, and just as there are two different materials used for shaping, there are different ways each one is primed. We'll start with a slump mold.

To prime a slump mold we use Primo Primer . It comes in a powder form to keep shipping costs low. It is very easy to mix, and even easier to apply. Mix the primer in a container with one part primer to four parts water, until the primer is dissolved in the water. I've found that warm or hot water helps the powder dissolve faster. I use a Hake Brush to mix and apply the primer because it mixes and applies faster. Ok, now that the primer is mixed you are ready to prime the mold. Wipe down the mold with a damp sponge to clean it. Use the Hake Brush to apply three coats of primer to the bisque. Allow each coat to dry before applying the next. I can usually apply the first two back to back, because the first coat dries very quickly. After all three coats are applied, the mold should be cured. To cure the mold, fire it at 550 degrees for 20 minutes. I’ve also had good luck setting the mold in the sun for a few hours or letting it sit overnight. You will be able to slump multiple times before you need to reapply primer.

Now, let’s look at stainless steel drape molds. This is even easier to do than the bisque molds. We use Boron Nitride to prime stainless steel. It comes in a spray can, so it's ready to use right out of the box. First, you need to clean the mold with rubbing alcohol. Second, you will apply two to three light coats of Boron Nitride. Just like the bisque molds, you should allow each coat to dry before applying the next one. The last step before draping your glass art is curing the mold. Curing the mold will make the finish more durable and last longer. Fire the mold at 200 degrees for 20 minutes. You can also let it air dry or sit overnight, but you may not get as many firings before you need to reapply the primer. Occasionally, the primer will become flaky and fall off of the mold. Just remove any remaining loose primer and reapply in those spots. That’s all there is to it!

Are you fired up? Good!

You can also watch these award winning videos*, done by yours truly, to see how to do each.



If you have any questions about this, let me know!


*may not be true