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FAQs for Glass Fusers

Amazingly, I’ve been teaching enthusiastic students how to work with glass for 36 years! I’ve helped thousands of artists create beautiful, unique pieces of art. Even after all this time I don’t consider myself an expert. I am very experienced, but like you I still have a lot to learn. It’s the glorious anticipation of learning new things that motivates and excites me to keep moving forward.

With my lengthy teaching history, you can imagine I get a lot of questions from students.  I thought I’d share some of them with you. I hope they help you understand different aspects of the craft and improve your fusing results.

Students constantly try to corner me and get absolute, it’s only done this way, fusing advice from me. My honest advice to them is this, there is no always or never in glass fusing. I approach every project with the intention of getting the best results possible. I will use any and all means and combination of materials I have at my disposal to achieve my goals. The following list in intended to be a helpful guide. There are many ways to approach glass fusing. Thankfully, for me anyway, it’s not an absolute science. That would take all the fun out of creating original art.    

Here we go:

Q.  Do you have to re-coat the ceramic kiln shelf with primer every time you use it? 

A. I do re-coat my ceramic shelve with primer every time I use it. I apply three coats of shelf primer on top of used primer. However, if the shelf shows signs of wear, I scrape it down to the bare ceramic with a single edge razor blade. I then re-coat the shelf with 3 fresh coats of primer. Visible signs of wear would include the primer looks thin, the coating has cracks in it or it’s flaking off the shelf.

Ceramic shelves ready to prime.

Q. Why does kiln wash stick to the back of the project?

A.This is usually the result of exhausted kiln wash; the shelf should have been re-primed prior to use. It may also occur when the glass has been fired to too hot a temperature or kept at full fuse too long. Kiln wash can be removed with fine steel wool or a scraping tool. Stubborn spots can be soaked off with a bathroom cleaning product used to remove hard water stains. 

Q. After the project is fused, how close to room temperature does the kiln have to be before opening the kiln lid?

A.How badly do you want the project inside? Room temperature is usually well below 100 degrees Fahrenheit. If you open the lid prematurely thermal shot can occur; breakage caused by changing temperatures too fast. Just a quick peek in the kiln, done too early can ruin your day. Wait, it will be worth it! 

Q. What causes tiny bubbles and how do I get rid of them?

A.Air becomes trapped between the layers of glass when it is heated. The number and size of the air bubbles can be reduced by heating the glass more slowly between the temperatures of 1000 to 1465 degrees Fahrenheit. This gives the air more time to escape before the glass edges become sealed.

Q. How do I avoid big bubbles?

A.Large dome shaped bubbles sometimes form in the middle of medium to large size projects. This is usually the result of firing too fast on a smooth surface like a ceramic kiln shelf. The outer edges of the project become soft first and form a “seal” like a suction cup on the shelf. Air becomes trapped under the glass. When it expands it lifts the glass and forms an unattractive bubble. This is less likely to happen when using shelf paper or a fiberboard kiln shelf, as the air can escape through the porous material. Best advice is to slow down the firing process. 


Q. Can I Stack kiln shelves?

A.Not recommended. Unlike ceramics, glass is thin and reacts to heat quickly. Stacking shelves causes uneven heating. The outer edges of the project become molten before the center has a chance to react; your firing results may be inconsistent.   

Q. How does the thickness of the glass relate to my target temperature?

A.A project made with two layers of thin fusible glass will usually reach the desired “look” before a project made with two layers of 1/8” glass. When you change project sizes or materials (thin vs. 1/8”) you will want to monitor the first few firings and make any necessary adjustments to your firing schedule.  

Q. Can more than one project be fired in the kiln at one time?

A.Yes, if the projects are similar. They should be made from the same thickness of glass, have the same number of layers and be close in size. Use a firing speed for the largest project. Small projects will not be harmed by firing slowly but the large project will suffer if rushed.

Q. What causes sharp edges on the project?

A.Dragging is usually caused by over firing a project that is resting on fiber paper. As the glass contracts and draws in on itself the paper resists, sharp edges are the result. This edge can be made safe with a file or grinder. After grinding the project can be put back into the kiln and heated until the ground edge is polished.

Glue between layers.

Q. Why is there debris between the glass layers?

A.Too much glue. Small amounts of glue will burn off leaving no trace. I avoid using glue if possible. When I do use glue, I apply a few pin head size dots on the backside of the glass. If you use an excessive amount of glue, it will burn becoming sealed between the layers, leaving dark blotches. Excess glue can also cause small eruptions that will blow a hole through the glass or cause pieces to jump and move in the kiln.

Q. What is the difference between using a ceramic kiln shelf or fiber paper?

A. Ceramic Shelf:

  • Fused glass will take on the texture/pattern of whatever it is fired on. If you fire on a ceramic kiln shelf your project will have a smooth back surface. (great for bowls, plates, fine art pieces; projects where a sleek underside is desired.)
  • A Ceramic shelf can be used repeatedly
  • A ceramic shelf is dense; it retains heat which allows the glass to pass through the critical stages slowly.
  • Ceramic shelves must be primed frequently; this can be time consuming.

  Fiber Paper:

  • Shelf paper comes in a variety of thickness and finishes. Generally, the thinner the material the smoother the fusing surface. (Great for coasters, pins, wall art; projects where a textured back side will make it easy to glue accessories on like rubber feet, pin back, etc.)
  • The thin material can only be used once. The medium material can sometimes be reused; it leaves a matte finish on the back of the project. The thick material can be used multiple times but the texture on the back of the project will be course.
  • The fiber paper is porous. Air can circulate, therefore large air bubbles are less likely to form between the glass and the shelf.
  • Shelf paper must be cut to size and can be costly if you are using it every time you fire.

Q. What are the differences between ceramic molds and stainless-steel molds? 

A. Ceramic Molds:

  • Ceramic molds come in a wide variety of sizes and shapes. They must be primed like the ceramic kiln shelf. The primer tends to last longer on a form than on a shelf because slumping temperatures are lower than fusing temperatures. Slumping occurs at approximately between 1200-1300 degrees.
  • Ceramic molds are inexpensive and durable, but they will break if dropped or used un-primed.
  • Ceramic molds should be sanded and be re-primed if there are pits or cracks in the primer coating.
  • Ceramic molds cool more slowly than the glass. Therefore, most molds are shaped so the glass slumps down into the mold, allowing the glass to contract first.

Stainless-Steel Molds:

  • Stainless steel molds come in a variety of shapes and sizes as well. They must be primed also. The slick surface makes priming more difficult. The mold can be sanded, sandblasted, or heated to make the priming process easier.
  • Stainless steel molds are extremely durable “forever” molds. But they tend to be several times more expensive than ceramic molds.
  • Steel molds should also be sanded and re-primed if there are pits or cracks in the coating,
  • Steel cools more quickly than the glass. The metal contracts underneath the glass which gives the room needed to slide the draped piece off the mold.
Ice Vase was made on this stainless steel mold.

A bit of advice:

Enjoy the creative process. Don’t rush it. Take your time. Make small test pieces to establish a relationship with your kiln and with fusing materials. Take before and after pictures. Take accurate notes so you can repeat the successful projects and learn how to avoid the failures. Don’t worry that the test pieces won’t be fun. Some of my best work originated as a small sample. Trust that as your confidence and skills grow, so will the size and complexity of your projects.

Wherever you are in your journey you are doing great! This is where you are meant to be in order to get where you want to go. Treasure every minute! 

Happy fusing!

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Make a Fused Glass Sink Webinar

April 21, 2022

Make a Fused Glass Sink Webinar with Lisa Vogt

You’re invited to join me for this comprehensive sink making webinar. In this LIVE event I’ll guide you step by step through the time-tested processes I use to make large-scale, functional vessels.

You’ll learn safe handling techniques for cutting oversized circles, how to fuse and slump thick pieces to retain consistent bowl height, plus trade-secrets for worry free drilling.

In addition to fabrication know-how, you’ll receive a complete supply list, specifics on kiln requirements, source information for the slumping mold and drill kit, as well as helpful installation tips.

In addition, I’ll demonstrate how to make a glittering dichroic sink. I’ll also show you how to make a cast glass sink from nipped glass pieces, dichroic bits and frit. Plus, you’ll be guided through the various cold-working steps I use to finish the cast glass sink edge to a glamorous, professional, quality polish.

With all the professional tricks revealed, you’ll gain the confidence and knowledge needed to make your own dazzling fused glass sink.

Fire & Ice


Make Fire & Ice!

Advanced Glass Fusing 4-Day, Hands-on Workshop May 24 – 27, 2022

In this class, you will push the boundaries art glass imposes. Students will explore innovative approaches to design and combine multiple advanced techniques to construct original art that reflects their own personal style. You’ll enjoy: the one-on-one instruction, making multifaceted projects, the well-equipped classroom, and the intimate class size.

You’ll love the concentrated, in-depth study and creative momentum you’ll gain while actively producing, nonstop for four consecutive days. You’ll leave class with a working knowledge of kiln operation, custom project specific firing guides, and the inspiration you’ve been craving to go bigger and do more elaborate works of fused glass art!

Join me for this intense workshop held in my private studio.
Wesley Chapel, Florida, 4-Day, Hands-on, Class size is limited.

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Artwear Mugs by Lisa Vogt

Get it now! Start fusing today!

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