Glass Fusing Q&A


No oneknowstheexactorigins of glass fusing although there is evidence that the Egyptians were familiar withrudimentary techniques. The Romans however arenoted by scholars for developingrefined glass fusing skills.

Although technology has changed the way modern glass fuserswork,the technique isessentially the same as those developed by the Romans centuries ago.

The basic technique involvesstacking two or morelayers of fusible glass, which are then placed in a kiln and gradually heated to between 1450-1500 Fahrenheit.At these temperatures the layers of glass fuse, or melt together and become one.

Unfortunately, glass kilnsare large andexpensive,whichkeeps most Hobbyists from pursuing this art form. Now there are new kiln options, including theThe Fuseworks Microwave Kiln. This device works in most household microwaves and can fuse glass in about 3 minutes. Here are some common questions we get on fusing in this modern-day kiln.

The following are Q A complied by Diamond Tech, the manufacturer of Fuseworks Microwave Kiln for the purpose of helping current users be successful, and to aid in the decision making of those considering the purchase of a microwave kiln.

Q: When I fuse my projects, sometimes I get medium to small bubbles. What causes them and how can I prevent them.

A: Bubbles can be caused by many different things. First, uneven stacking of glass can result in air trapped between layers. To prevent this from occurring, check the placement of all the glass pieces and insure they are sitting properly on the base. Since the edges of the glass fuse before the center of the glass, cut your base glass 1/8 larger than the top layer to allow air to escape.

Second, check the glass prior to fusing. Some glass may already contained bubbles inside the glass, which may or may not affect the outcome.

Q: After I fuse my pendants, I get uneven areas around the edges. Whats happening with the glass?

A: You did not fire it long enough or to a high enough temperature for a full fuse. Try firing at a little longer time.

Q: Sometimes my glass pieces look like a porcupine with spiky edges. What causes the glass to spike?

A. Spiky edges can be caused by over-firing your piece. The spiked edges are caused by the glass grabbing as it is trying to shrink.

Q: What caused my layered glass pieces to flatten?

A: If the glass piece has flattened out too much, you have over fired the piece. To prevent this from happening, reduce your power and shorten your time. After your first firing, open the microwave and using Fireworks Hot Mitts, carefully lift the lid to inspect the fuse piece. If the desired results has not been achieved, continue firing in 30 seconds intervals.

Q: I tried to make a 1 inch pendant with embellishments, however after I finished fusing, the glass shrunk. How can I prevent this from happening the next time?

A: Glass naturally wants to be inch thick when heated. Your glass will shrink or expand to obtain this depth. A good tip to remember is that if your piece is less than inch when you start, it will shrink up to reach this depth. If your piece is larger than inch when you start, it will want to flatten out to reach this depth.

Q: What causes two pieces of dichroic or iridized glass to blow apart in the kiln?

A: Repelling glass will occur with dichroic and iridized coatings. The coatings cant be placed together for fusing purposes, because they repel each other. The only way to avoid this is to encase the coated glass with a non-coated glass, such as clear. This will cause the coated glass to be encased and sealed.

Q. Yuck, this film appeared on my fused glass. What is it and how can I prevent this from happening?

A: This dull white crystalline substance on the surface of your glass is known as devitrification. This is one of the most talked about glass fusing problems around. It can occur when your glass remains in a temperature range 1000F-1300F too long. You need to minimize the time spent in this temperature range.

Q: I notice gray or scummy edges appear after a use my grinder or saw to shape my piece.

A: Gray or scummy edges can occur on pieces that have been fired once and then cold worked before refiring. Cold working involves using either a grinder or glass saw on a piece of glass. These can be avoided by thoroughly cleaning the glass before refiring the piece. Keep a bowl of clean water near your work area and soak the glass right after doing the cold work procedure. This will keep the edges damp and allow the piece to be cleaned easier. Scrub completely and let dry before proceeding with the refiring process.

Q. My glass cracked! What happened?

A: Cracking glass either during or after firing can be caused by a several things: thermal shock, heating up the glass too fast and compatibility.

Thermal shock occurs either by taking the piece out of the kiln too soon, or by opening the kiln and exposing the hot glass to cool air. If the glass cracked in the kiln and it has an S shaped crack, the piece has heated too quickly.

Slow down! Finally, If the crack occurs along the line where the two pieces of glass meet, then the two touching pieces are not compatible. Make sure the glass you are using have the same COE (coefficient of expansion).

Q: How can I prevent my glass from shattering?

A: Glass Shattering in pieces over 1 with more than 1 layer may sometimes shatter. To prevent this from occurring, reduce the power this allows the glass to heat slower and is less likely to shatter. Next, make sure your glass is clean and dry before firing.

Q: My fusing instructions say to clean my glass before firing, can I use an glass cleaning spray or detergent?

A: We dont recommend it. Detergents, dish soaps, multi-purpose cleaners, some window cleaners, ammonia and even denatured alcohol should NOT be used to clean glass. These can actually promote devitrification. We suggest diluted white vinegar or rinsing your glass with distilled water.

Q: Every time I put my fuse glass project together, the pieces roll off before I can get it to the microwave. What can I do to prevent this from happening?

A: To hold your fusing project together, mix one drop of white glue to three drops of water (a 1 3 ratio). Apply a very thin amount the back of the glass using a brush and allow the glue to dry thoroughly before firing.

profile image
Bella G.  •  July 04, 2021
I contoured fused a small flag and it finished with a large hold in the center of the project. I used COE sheet glass and frit. Here was not a hold in the glass can me what happened. Thanks
profile image
Rosanne R.  •  August 01, 2020
I am new at this. Using a michrwave kiln. have made some good piece but having problems today. Black base, dichroic pieces for middle layer, then clear top. Came out looking completely black - dichroic disappeared. Ideas?
profile image
Joan M.  •  June 29, 2020
Does the base glass have to be all one piece or can it be several pieces prior to fusing. Like I have a fish pattern which the tail and fin r separate for base glass and then the colored glass placed on top. Full fuse will tail and fin fuse to body of fish or do I have to cut all one piece?
profile image
Joan M.  •  June 29, 2020
Does the base glass have to be all one piece or can it be several pieces prior to fusing. Like I have a fish pattern which the tail and fin r separate for base glass and then the colored glass placed on top. Full fuse will tail and fin fuse to body of fish or do I have to cut all one piece?
profile image
Edith K.  •  March 02, 2020
Do the devitrification liquids that r sprayed or brushed on of any value? If you have already fired your piece n have dull spots will using this stuff help? Should the liquid Bu applied b4 fusing, just in case? I belong to a club that fires many pieces 2 gather...
profile image
janet e.  •  June 25, 2019
two questions: can pieces be fired more than once in a microwave kiln (cooled then refired)? Also, can glue be used in a microwave kiln?
profile image
joe v.  •  July 18, 2016
I got a question. How can you make the bottom of the glass( the side that in on the shelf) smooth as the top?
Diamond Tech Crafts

Diamond Tech Crafts

Where We Were Then Diamond Tech’s founder and CEO, Dan F. Daniels, has a firm belief that a creative life brings people towards inner growth as creative thoughtful individuals and tolerant caring members of a community. He has strived in every aspect of his business life to work towards these goals by fostering the creative arts through mosaics, glass fusing, lampworking and stained glass.   With over 30 years in the glass arts industry, he created Diamond Tech. For 15 years Diamond Tech manufactured products for the stained glass industry; then in 1998 we entered the craft market with Jennifer’s Mosaics a complete line of mosaic glass, tools and supplies.   In the years that followed, Diamond Tech added such popular brands as Studio Pro, Fuseworks, Fireworks and KraftyBlok to its line of glass crafting products. Jennifer's Mosaic products have won Crafts and Craftrends Awards of Excellence and in 2008 Fuseworks won a CHA Innovation Award.   Where We Are Today Today, Diamond Tech is the place to find and discover the country’s best quality stained glass, hot glass and mosaic tools, and accessories. We value our customers and we will bring only the best quality products at the best possible value. Diamond Tech understands the needs of our customer and constantly strives to acknowledge and fulfill those needs in every possible way.   Diamond Tech is very proud to be a contributing factor to the promotion of the creative arts industries. We look forward to contributing to a better world through crafts.