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Firing Surfaces – A guide for beginner to advanced fusers.

Okay, you’re thinking I’ve run out of hot topics, if I’m writing about something as trivial as firing surfaces. But firing surfaces have a significant impact on the physical appearance and manufacturing cost of your finished fused glass artwork. In my experience, those two important factors make further study into the best practical uses of the many different options worthwhile. So, let’s get to it.

Firing on a ceramic kiln shelf.

Ceramic Kiln Shelf:

The advantages of using a ceramic kiln shelf are many. A well primed (kiln washed) ceramic self will give the backside of your fused glass a smooth, professional looking finish. Re-priming a ceramic shelf is fast and easy. Plus, doing so makes little dust or mess. (I prime my ceramic shelves with 3- 5 coats of primer before every use.) And using a primed shelf is the least expensive, most cost-effective way to fire glass.

One disadvantage to a using a ceramic shelf is the primer’s dry time. You can speed up the dry time by placing the wet shelf in the sun or by heating it in a vented kiln set to 500 degrees for 15 minutes. (Be sure to let the shelf cool completely before placing any glass on top.) Another drawback is weight. Ceramic shelves are heavy, so moving them in and out of the kiln can be awkward. Size is another thing to consider. Ceramic shelves tend to be cut considerably smaller than the kiln’s interior therefore reducing the number and size or projects you can fire at one time. By cutting a larger, tighter fitting kiln shelf from fiber board, you can increase the number and size of projects that will fit.  

Firing on a fiber board kiln shelf.

Fiber Board as a Kiln Shelf:

The fiber board we’re referring to here is a high refractory material purchased at your art glass supplier specifically to use inside a kiln. It’s available in a variety of sizes and thicknesses. The sheets I use are ½ inch thick, 24 inch wide and 36 inch long. This fiber board is primed with 3-5 coats of primer before every use. The pros: it’s lightweight and cuts easily to fit tightly inside any size kiln to maximize the firing space. It becomes smoother with every coat of primer and soon produces a finish that is close to the smoothness of ceramic.

The cons: the porous material retains moisture like a sponge, therefore its flimsy when wet with primer (so moving it when wet is not recommended) and it takes longer to dry than ceramic.

White glass, and some paint-based labels like those on the backside of Grey Goose bottles, will stick to the board even if it’s well primed. Removing white based projects will pull a chunk out of the board. I fire these projects on fiber paper or primed ceramic to avoid damaging my fiber board shelves. 

Fiber board is soft. Dropping glass or another hard object on the shelf will put a hole in the smooth surface. The upside is damaged shelves can be cut down and used for shelves in smaller kilns. Or they can be cut into strips and used to dam cast glass projects. Nothing goes to waste.

Fusing on Fiber Paper:

This is special paper purchased at your art glass supplier for kiln use. It’s a convenient material designed to act as a release between fused glass and the kiln shelf. Fiber paper comes in a variety of thicknesses.

Firing on fiber paper.

Thin Fire looks, feels and cuts like regular paper. It’s identifiable by the name printed on the backside. This is a convenience product that delivers a nice smooth finish. It’s ideal when you want to quickly swap projects in and out of your kiln without having to prime shelves. The disadvantage is cost and clean up. Thin fire costs several dollars a sheet. It’s a onetime use product that turns to dust after fusing. Clean up involves vacuuming the left-over material out of your kiln.

Thin fiber paper is slightly thicker than thin fire. It has a smooth side and a textured side. Even the smooth side leaves a slight pattern behind on the backside of projects. If handled carefully, you can get more than one use out of the paper. I like to use it to emboss patterns in the bottom of my artwork. I cut shapes out of the paper with scrapbooking punches. The project it assembled in the kiln on top of the cut outs and fired. It’s a fun, easy way to add detail to your work. The disadvantage to using this material to cover a kiln shelf is the texture it leaves behind and the cost it adds to the fabrication. Clean up involves vacuuming the spent material out of your kiln.  

Firing on 1/8 inch fiber paper.

1/8 inch Thick Fiber Paper is stiff enough and durable enough to contain thick glass during the fusing process. I cut it into strips and use it to hold cast glass projects in place. The nice thing is that you can design your own custom shapes and sizes without being limited to ready made casting molds. It can also be used to make deep, ornate embossing patterns, in the backside of your artwork. If handled carefully, it’s possible to get more than one use out of this paper. Due to the added cost of this thicker material, it would be used to cover a shelf only for specialized purposes. Another drawback to this paper is the visible texture on both sides. Like it or not, this paper leaves a noticeable impression in finished fused glass projects.     

Firing on fiber blanket.

Fiber Blanket: This material is very versatile. It comes in several thicknesses that have multiple uses. I use it to cover the kiln shelf when I want to create a project with rustic texture and a wavy free form edge. It’s also flexible enough to drape over slumping molds to achieve organic shaped pieces of art. It can be primed to give your art a shinier finish or left raw for a frosted finish. Stored carefully, his material is very resilient and can be used in any number of ways repeatedly. Fiber blanket costs more than the other fiber materials, but it’s worth having a sheet in your studio due to its durability and for its experimental value. 

When deciding on a firing surface, I consider what I what to accomplish with a particular project and then select the best surface to achieve that outcome. I’d recommend having all these materials on hand. Then, when a unique project presents itself, you’ll have the flexibility to fire it on the surface best suited to create your desired effect.  

Happy Fusing!


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4 thoughts on “Firing Surfaces – A guide for beginner to advanced fusers.

  1. Hi Lisa. I struggle with kiln washing my ceramic shelf. Do you clean/sand/wipe your shelf every time you kiln wash it? I cannot figure out what I am doing wrong. Thank you for your help. And all of your ideas and advice. I really appreciate it.

    1. Hi Stephanie, I prime my ceramic shelves right over the used primer every time I use the shelf. If the used primer has cracks in it I scrape the shelf clean then re prime it with 3 – 5 coats of kiln wash.

  2. Lisa,
    You said that you put an additional 3-5 coats of primer on the kiln shelf before each use. I am assuming that you put the new coats of primer on top of what is already there. How often do you completely remove all the old primer on the shelf and re-coat it?
    Thanks for all your tips and instructions. You are a great teacher with lots of talent. I appreciate everything I have learned from you.

    1. Hi Cecile, I prime my ceramic shelves right over the used primer every time I use the shelf. If the used primer has cracks in it I scrape the shelf clean then re prime it with 3 – 5 coats of kiln wash. I remove all the primer every 3-5 times I use a ceramic shelf. It depends on the firing temp I use. Hotter firings like 1600 degrees instead of 1465 will cause the primer to become thin or crack. Thanks for your encouragement! Happy Fusing, Lisa

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