Fused Glass With Plaster Forms

If you haven’t tried fusing with plaster forms yet, you should give it a try. The main idea is to create a small three dimensional plaster form and then fuse glass over it. After fusing, the plaster can be removed leaving a detailed copy of the plaster form in the glass.

Today we’ll make a set of reference pieces to have on hand for future project planning. I always start a new technique with a set of reference pieces, my ‘library’ has hundreds of sets now, and they come in quite handy. I highly recommend the practice.


Plaster of Paris (available at hardware and craft stores)

Latex, rubber or silicone mold (try the cake decorating department at the craft store)


Measuring Spoon


Flat bottle glass in desired colors for reference

Plaster of Paris forms materials

Plaster of Paris materials

Most Plaster of Paris is mixed 2:1, two parts plaster to one part water. My mold uses just a tiny bit of plaster, so I’m making a very small batch.

Step 1:

Measure out the plaster

measuring Plaster of Paris

Plaster of Paris

Step 2:

Measure the water and add it to the plaster

Making Plaster of Paris

Water for Plaster of Paris

Step 3:

Mix. It helps to give the plaster a minute to absorb the water and become saturated. With such a small batch though, don’t wait too long!

Mixing Plaster of Paris

Mix Plaster

Step 4:

Add mixed Plaster of Paris to the mold

Plaster of Paris forms

Plaster in the mold

Once the mold is filled, tap the side with the spoon to help any trapped air bubbles escape.

Step 5:

Repeat as necessary for the desired number of Plaster of Paris forms to fuse with your test glass. I’m using two layers of bottle glass in all the different colors I normally fuse with.

fusing with plaster forms

Plaster forms for glass fusing tests

Step 6:

Place two layers of glass (to equal 1/4″ thickness) on each plaster form on a prepared kiln shelf:

Fusing with Plaster Forms

Testing Plaster Forms

Step 7:

Fire to a full fuse using the fusing schedule.

Fused Glass on Plaster Forms

Fused glass on Plaster Forms

After fusing, you can easily remove the plaster from the back of the glass pieces with a scraper or dental tool. The Plaster of Paris should begin to break down and become quite soft during the fusing process. If it is difficult to remove, add water or diluted vinegar to encourage the plaster to break down.

Once your test pieces are all clean, you can see what each color looks like fused with a plaster form, and use them to make future design decisions.

Fused glass with plaster forms

Fused Recycled Glass with Plaster Forms

fused bottle glass with plaster

Fused bottle glass with a plaster form – detail