HackSpace magazine

Microwave Kiln Review

By Ben Everard. Posted

Working with glass usually requires thousands of pounds worth of equipment to carefully heat and cool the material. However, what if you could bypass all this and just pop it in a microwave?

It’s not quite that simple, because glass itself doesn’t absorb the frequency of microwaves used to cook food, but that’s where the microwave ‘kiln’ comes in. This device is basically a box made out of high-temperature resistant insulator, with a lining of a material that absorbs the microwaves and converts them into heat.

There’s a small central section where you can put the glass you want to heat, then the lid goes on, and the whole lot goes in the microwave.

We bought a 12 cm kiln from July Tool’s Store on AliExpress for £15.92, including shipping to the UK. We also got 50 sheets of kiln paper (£5.10), which is needed to stop the glass from sticking to the bottom of the kiln when it’s melted.

12cm is the outer diameter; there’s actually only 7.5 cm of space to work with, and as you don’t want your object too close to the edge, there’s about a 6 cm diameter of workable space, but as the heat isn’t evenly distributed, you’ll get better results if you stick to 3–4 cm diameter objects.

Our biggest concern was whether the kiln would get up to temperature for melting glass, and it managed this in our 900 W microwave. We measured the temperature at 690 °C , but we should note that this is at the absolute top end of our IR thermometer, and it was struggling to get a temperature – this was the temperature after we’d taken the glass out of the microwave, removed the kiln lid, got the thermometer into action, and lined up for the test. Basically, we’re saying that it gets quite a bit hotter than this.

While we can’t give temperature ranges for it (and they will vary by microwave), in our experience, the kiln is hot enough to get the glass up to a temperature where basic working is possible, and separate pieces will melt and fully combine together.

Cooling glass, still glowing orange from the heat

When it comes to glass-work, getting up to temperature is only half the problem. Cooling the glass down slowly enough to prevent it cracking is also a challenge. However, our insulated box works for this as well. Once you’ve heated your glass up and fused it, the sealed box will slowly cool over about an hour. For small pieces of work, we found that this was slow enough not to cause cracks as it cooled.


There are several different ways you can work glass in a
small kiln such as this. You can place the glass on top of a object and let the glass soften and take shape around this former, or you can place two bits of differently coloured glass together and fuse them to a new piece. You can even heat the glass up and manipulate it with a metal ‘rake’ to create swirls and other effects. We managed all of these to a greater or lesser extent.

By placing shapes under the glass, you can leave impressions in the finished glass-work

Lots of different types of glass can work with a kiln such as this. We had some success using glass from old bottles - in general, we found the glass was a little thin and the curves made it hard to stack, but thicker bottles, such as those used to store fizzy wine, worked better.

The colours in bottle glass are usually quite muted. You can get much more highly coloured glass that’s designed specifically for crafters.

We don’t have space here to get into the full details of how to use this kiln effectively and safely, but there are some things you’ll need to consider, including proper protective equipment (these temperatures are incredibly hot, and you need to be appropriately careful).

Some of the materials you may use can give off dust which you really shouldn’t be breathing in when handling. If
you do plan on using a kiln like this, make sure you fully understand the challenges beforehand.

While we had great fun testing this out, the results were mediocre. Without the ability to control the temperature of the kiln, there was a lot of trial and error, though ultimately, we were able to get it to about the right temperature.

A bigger problem was that the heat wasn’t evenly distributed, so the middle of our work got hotter than the outside, which led to some uneven melting.

Ultimately, you can create fused glass with this, though it is a bit of a slow process to learn how to get good-looking fused glass. Over time, we’re confident we could have learned better ways to work around the limitations, but these limitations are still going to be there.

In short, this microwave kiln is a fun tool for exploring simple glass-work, but it’s very limited. For the price, it’s a great investment if you want to have a go at the basics – and if you’re persistent, you’ll probably be able to create some good-looking glass-work.