Fused Glass – Quality and what you should be looking for

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If you encounter any problems, please email me at hello@vividluxglass.co.uk

Thank you!


Welcome to my new blog! I haven’t written a blog post in 3 years…but I hope to bring you more posts from now on. If you have any ideas for posts or questions you’d like me to answer, get in touch.

Fused Glass – What is it?

For more information about what Fused Glass is and isn’t, I’d recommend reading the About Me page. It has lots of information about the glass I use, limitations, different types of glass and information about annealing, firing etc.

When buying fused glass, what should you look out for?

Oh, I’m glad you asked! 😊

Fused glass comes in many shapes, sizes, forms, colours! There are many really great quality glass artists out there. Unfortunately, there are some not so brilliant quality, too.

The main things to consider are listed below. I’ll expand on each point in turn.

  • Strains/Stresses in the glass
  • Dogboning (yes, a real term :D)
  • Bubbles
  • Finishing – Drilling, hooks, sharp edges

Some of these are poor aesthetic quality, others could become a quality concern.

The photos below are all my own work from the first 6 months working with glass (except the incompatible glass photo). I’ve been fusing for nearly 5 years now. In the years since I started, I’ve learned so much! Things still go wrong from time to time but every day is a learning day! I’ve kept all my disasters with notes so that I know what went wrong and what to change for next time.

Strains/Stresses in the Glass

There are several causes of this. If the piece hasn’t been annealed correctly, at the right temperature or for long enough, this will cause stress/strain within the glass and it is likely to crack or shatter (see About Me for more information about annealing).

Stress within glass can be evident short term or much longer term. I’ve heard of pieces of glass being fine for 10+ years and then suddenly one day they’ve suddenly cracked or shattered. This is down to not being annealed properly when first made. Unfortunately, you don’t usually see these types of strains until it’s too late.  Rest assured I anneal everything properly, for the correct time, temperature and depth of glass (because the size also matters when annealing!)

Incompatible glass causes cracks. There are many types of glass available but not all can be fused together! Beginners often make the mistake of using say Bullseye glass with bottle glass – this is a definite no. The glass you fuse MUST be in the same “family”. Even fusing 2 bottles together which were made in the same factory isn’t recommended because different bits of glass are used.

You can fuse a shattered windowpane or photo frame glass to itself but you can’t mix it with any other glass and fused it. This is why I mainly stick to specialist art glass. I know it has been tested compatible with the rest of the range.

There are tests that artists can use to check for strain within the glass, most use polarising filters and a lightbox to check for signs of strain when using float (window/bottle) glass. Any stress/strain shows up as white halos or milky white haze. If using specialist art glass, this test isn’t required.

The photo below shows what happens when you fuse different types of glass together. 

 Here you can see the result of incompatible glass being fused together in the kiln. The crack doesn’t usually run all the way through the glass but it is very noticable. You can clearly see the stress in the glass, formed as cracks around the blue. You absolutely wouldn’t want to buy this!


This describes a piece that has been either over-fused, meaning the edges are (proper technical term here) “dog-boned” or the glass hasn’t been cut accurately enough. Sometimes it also happens when only 1 layer of glass has been used and it has been fired too hot in the kiln. It’s usually very noticeable on squares and rectangles.

 This piece is fine. It’s not perfectly square but there is no dogboning going on.

I had to digitally manipulate this photo as I don’t have any examples! But here you can see the straight sides have pulled in towards the middle, leading to the dogbone effect. It is really common to see this. 

Sometimes it’s not very noticeable but a lot of the time I see artists selling their work like this. It’s such an easy thing to fix by grinding the edges straight and popping back into the kiln for a “fire polish”. Or y’know, remaking it, seeing as though someone is paying for it :/

Sometimes this effect is part of the design, especially with bowls, plates etc. But generally anything hanging, like a suncatcher, shouldn’t really look like this.


Oh bubbles. The bane of a fuser! Bubbles are pretty inevitable. Even with a good “bubble squeeze” schedule. But different bubbles mean different things!

“Champagne” bubbles are totally normal. Pretty much most fused glass will have tiny bubbles. Air gets trapped between the glass when the heat seals the edges of the glass. A bubble squeeze segment can be added to the kiln schedule to combat bigger bubbles from forming but chances are, there will always be tiny bubbles!

Some bubbles are formed when using inclusions within the glass. So things like copper, brass, wire, fusing glitter etc – Most of the time they end up being exactly where you don’t want them! Check out these pieces below. I can’t sell these as the quality is not up to my standards so they sit in a box as a lesson not to do it the same way again!

Of course, sometimes we like to add bubbles! In that case, there are different products we use. There are special bubble paints that can be fused within two layers of glass. I like using Copper Oxide as it gives a beautiful blue colour. Bicarbonate of soda is often used by artists too. The examples below were made using copper oxide powder and bubble paint. It’s quite difficult to control though and you don’t need much to produce the pretty bubbles. If you use too much, you get bigger bubbles that sometimes distort the glass.

Sometimes huge bubbles can appear in glass. I’ve not had it happen yet, luckily! With big bubbles, the base of the glass is often stretched thin, meaning there is a chance it could break. Apart from huge bubbles, quality wise there isn’t really anything wrong with having bubbles. It’s more of an aesthetic thing. I prefer not to sell my work with the larger bubbles as it detracts from the design.


When I first started out, I did not want to drill holes in glass. It was such a scary prospect to me! Now, nearly 5 years in, I wonder why I was so scared because they’re actually really easy to do with the right tools and know-how!

Many glass artists use metal wire – sometimes copper, sometimes high temperature nichrome wire. I find copper a bit too soft. Once it’s been fired in the kiln, it goes black but it can be cleaned. Unfortunately, if you need to bend or twist the copper, or if it’s use to hang a piece for a long time, it generally snaps after a while because it’s such a soft metal. Nichrome wire is better to use, though not as nice looking! When buying a fused glass piece with wire fired inside the glass, you need to look out for any stresses where the wire is. 

Also, the wire should be bent or curved within the glass. Straight wire will likely fall out as it’s effectively only sandwiched between the glass, not actually stuck to it, so a straight piece can (and often will) slide right out. With a bend or curve in place, the wire can’t slide out as the glass has sealed around it.

Example of a curved hook, sandwiched inside the glass.

This piece went wrong in many ways! But the hooks are firmly in place, and have been  for 4 years!

Lastly, there should be no sharp edges, points or burrs. Sometimes, depending on the design, the glass might be slightly rough to the touch but it should not be sharp.

Glass fusing is not a quick process. You have to have patience. Kiln schedules can take 24 hours or more, so I know why artists are reticent to remake or fix things sometimes. But if people are paying for your work, it has to be of a good standard, in my opinion. My standards are set high, but I’m human, I do get things wrong sometimes! When buying from Rainbow Lux Glass you’re not just buying a piece of glass. You’re buying part of me, my training and knowledge, you’re buying something that should last a lifetime (and more), you’re buying something special that isn’t available in the shops.

So there we go. Hopefully you’ll know a little of what to look out for when buying quality glass in future. It’s by no means an exhaustive list, just some general pointers. I hope this has given you an insight into my fusing world!

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