It only takes a few minutes in your regular microwave oven, to heat up this microwave kiln to temperatures hot enough to fuse glass or even melt metals Before I show you how to make a microwave kiln Let me better explain what it is Microwave kiln is… a kiln But it doesn’t use gas or wire heating element to heat up instead it uses microwaves Inside of the microwave kiln you’ll find silicon carbide Silicon carbide absorbs microwaves, does heating up to very high temperatures microwave Kilns are probably most popular between people who fuse glass You can turn pieces of glass Into amazing jewelry, but that’s not all there’s so much more you can do with microwave kiln you can fire ceramics and you can even burn out wax or PLA from plaster molds when doing metal casting and yes, you can melt metals But that’s for another article because there’s a better way to do it than using just a microwave kiln In this article In this article I’ll demonstrate how to make a small three piece microwave kiln and at the end of the article I’ll show you some other kilns I made and tell you how they differ You will need to make a plaster ring To do that you can make a mold from eva foam and then fill it with plaster If you have a 3d printer You’ll find links to different size molds you can print You also find some affiliate links to materials I used and a link to this printer It’s important to make your plaster ring weak It can vary from plaster to plaster, but in general you want your plaster mix to be quite watery After one hour the plaster is ready for the next step Put it in a microwave on top of some paper towels Microwave it until most of the moisture is gone. I know my microwave so I don’t touch it until the plaster is dry Since you’re doing it for the first time you can always stop the microwave to wipe it down and make sure it doesn’t get too hot And by the way, this is not the way you normally cure the plaster Microwaves will make the plaster weaker, but in this case it’s okay You’ll want to close one side of the Ring with a lid or something of that sort Electrical tape works great because it’s stretchy If you use the 3d printed mold just flip the base around and use that You’ll want to make a mark on the side of the ring.

You’ll see for what in a second You’ll need sodium silicate also known as water glass The one I have right here is 37% But you can also use 40% it’s not gonna make a big difference Here is cured sodium silicate with some food coloring added to it As you can see it looks like glass You’ll need to mix sodium silicate with water in ratio one to two by weight In this case I used 11 grams of water glass and 22 grams of water Then I put it in a small spray bottle You will also need silicon carbide grit Here you can see three different grid sizes for comparisment I used 80 grit silicon carbide but different grid sizes will also work just make sure it’s not too powdery like four hundred or too coarse like 24 grit First we gonna wet the walls with water and let it soak for a minute Then we will coat them with silicon carbide grit Use your finger to press it down Then we’ll spray some water glass and coat the plaster with another layer of silicon carbide Make sure to press silicon carbide tightly together You don’t need to spray water glass after every layer Do it by the feel Silicon carbide should feel wet but not too wet On average I spray it every second layer The mark I left with the permanent marker helps me to see when I have sprayed a full circle That way I don’t over spray the water glass When desired thickness is achieved you can use a popsicle stick to remove the excess silicon carbide Now we can remove the bottom Will tidy up the other side Press it down very well and if necessary Spray some more water glass Later in the article, we’ll need some ceramic fiber insulation blanket Also known as Kaowool. We’ll use some now to insulate the ring and protect the microwave Make sure to wear gloves and a respirator when handling it We’ll microwave the ring until it glows red We’ll take it out, remove the top blanket and let it cool Once cooled you should be able to peel off the plaster If your plaster is too strong, when it cracks it will also crack the ring You’ll need a piece of glass, a glass from a picture frame will do just fine We gonna pour some silicon carbide on top of the glass and we’ll add some water Then we’ll use a drinking glass with a flat bottom to sand it It should look like this Will spray tiny amount of water and we’ll sand the ring In case you missed it.

I sprayed water not water glass After dusting it off. weaker, but
I put it in a microwave to dry it This is the point where you can spray some more water glass to make the ring stronger just don’t overdo it A quick microwave dry and our ring is ready It weights about 40 grams and is four millimeters thick Here’s a failed ring with too much water glass The water glass bubbled up and cracked the silicon carbide.

I cut two strips of ceramic fiber blanket I parted one strip in half because I want to keep my kiln small Then I cut one end of the strip in angle I wrapped the ring and did the same thing with the other end Then I did the same thing with the other strip I used rubber bands to keep ceramic fiber from unwrapping Give it a roll to make sure everything sits in place nicely We will use water glass again. But this time you don’t need to add water Instead.

We’ll add some food coloring We’ll glue the end of the strip to keep it from unwrapping Pay attention. I’m not brushing it under the blanket only on top More on that later. I put it in a microwave to cure water glass If you use food coloring It will most likely go brown If the rubber bands didn’t break in microwave, now it’s time to remove them Next we tightly wrap the kiln with a cling film I cut off the excess plastic from the top and the bottom Will use the glass again, but this time to sand the kiln Use generous amounts of water and start slow Once the water is absorbed you’ll be able to move the kiln easier As you can see I have wrapped the table with a cling film to stop the glass from moving Once sanded, it should look like this Now we can microwave dry it After removing the cling film I cover the rest of the kiln with more water glass I did it in two parts, so the kiln wouldn’t stick to the blanket After microwave curing it, I did the other side Until the kiln is ready.

Don’t overheat it in a microwave when curing water glass I’ll tell you why later. was hot from previous use
I use the heat gun to heat up water glass and change its properties then I switch to a blowtorch Using a heat gun is optional if you have to choose one Choose blowtorch just make sure not to overheat the kiln in one spot Some parts of the kiln will look like a popcorn ceiling. You don’t want too much of this effect So we’ll send it a little bit I’ll tell you why we’re doing it later.

I mix the leftover water glass with water in parts 1 to 2, then I brushed it on a kiln After a quick microwave dry, I added another layer and dried it again Then I cut one of the holes bigger I sand at the top and the bottom again and microwave dried the kiln for the last time Then I put it on top of two ceramic blankets so I could cut out the shape I sprayed some water between the blankets so they would stick together better while I work on them After covering the sides and top with water glass. It was microwave cured This time I didn’t use a cling film because we’re sanding the blanket the flat side down Cling film was used to hold the layers of fiber together.

I decided to add some more water glass And then the same procedure again heat gun and a blowtorch or only a blowtorch Then I got rid of the popcorn by sanding it I covered it with one to two ratio water glass solution After microwave drying it it was sanded again I used two packets of sugru to add silicon feet After making sure it was straight. I let the sugru set for 24 hours The same way I made a lid but it’s only a single blanket thick That’s it, our three part microwave kiln is ready Here I have some glass from broken bottles Let’s fuse it You don’t want to put the glass directly on the base or it will stick to it We’ll use these fiber paper sheets that are made for this purpose Firing times will depend on your microwave and the size of your kiln In this microwave it takes about four minutes to fuse the glass.

I don’t use gloves because the outside of the kiln is just warm It will get hot after a few minutes. But by that time the kiln will be resting Let’s see how it turned out Let’s speak about the glass turntable should you use it? Hmm… in some microwave ovens glass turntable can absorb some of the microwaves does heating the kiln slower. some more water glass
It’s especially true when the plate is hot.

So here’s the situation You finished fusing glass and you want to use your kiln straightaway. The kiln is still warm. much of
So you think all right because it’s warm, it will probably need less time in microwave to fuse the glass so you put it in a microwave only to find out that it actually needed more time than usual So what’s happening?

Turns out the glass plate was hot from previous use Because it’s hot now it will start to absorb more microwaves more microwaves that absorbs, hotter it gets Hotter it gets, more microwaves it absorbs Here’s a quick demonstration If you heat up the plate in one spot with a blowtorch, it will keep heating up in the microwave It’s good that I didn’t need it. This 800 watt microwave can fuse the glass in less than three minutes If I use it with a turntable, it will take closer to four minutes A thousand watt microwave would do it even faster Of course heating up the glass that fast is not always the best thing to do In fact, sometimes it’s better to turn down the microwave power to achieve better results This three-piece microwave kiln can be abused Let me explain A lot of popular microwave kilns are made similar to this one In this kiln silicon carbide is directly glued on walls with time because of heating and cooling differences of these materials the silicon carbide will crack And kiln can also crack that’s why you don’t want to open these kilns to cool them while they’re still hot Because that’s a quick way to crack them This kiln is made differently if you made a mistake and you want to cool the kiln as fast as you can You can just flip it on side while it’s still hot and it’s not gonna crack Because of ceramic fiber and water glass kiln weights less than a can of coke and the water glass It’s pretty hard So, why did we sand the popcorn pattern and why did I say that it’s better not to put any water glass between ceramic fiber sheets Well, it’s to prevent the water glass from heating up on its own and to avoid a possible microwave arcing Just like with a glass plate the water glass can heat up on its own and damage your kiln Here I recreated the problem the part that is glowing is not silicon carbide It’s water glass As we discussed before Water glass kind of looks like glass add some weird popcorn patterns And you have increased possibility of microwave arcing and kiln heating up in random spots That’s why we used a blowtorch to make the kiln look more like stone and less like glass It’s also why I don’t recommend brushing water glass between ceramic fiber blankets because you won’t be able to heat it up to make the water glass appear less glass like it doesn’t mean that you’ll always get this problem Some of my early kilns have glued fiber sheets and popcorn pattern and they worked just fine But you never know.

That’s why it’s better be safe than sorry Here’s another popcorn light kiln I made As you can see I didn’t even bother to cut the sheet in angle. I have used this kiln quite a lot I mainly use it to burn out wax or or PLA from plaster molds and as you can see there are three large rings But how do you fit it in a microwave?

Well, you just flip the microwave on the side As you can see there’s actually space for even a bigger kiln This is what happens when you don’t use a fiber sheet The glass has stuck to the bed. If you try to remove it. You will make a hole in the base Well, actually it’s not too bad so let’s make some more holes WHAT??

I’m just showing you how easy it is to fix the base if it’s damaged A quick water sand on top of the glass and your base is good as new Let’s address two questions that people normally asks Is it safe to cook food in a microwave that was used to fuse glass? I don’t see any problems at least with a kiln like this one Of course, if you’re planning to use the kiln a lot it only makes sense to get a dedicated microwave But if you just want to play around It’s okay to use the same microwave as long as you make sure it’s clean well-ventilated doesn’t have any weird smells and is not damaged Which leads us to the next question. Can I damage my microwave? Let me answer with facts in the last year I made over 100 kilns I’m not kidding Here are some of my early prototypes After trying more than hundred kilns I can confirm that I broke zero microwaves The only thing I recall, is burning the paint with a hot fire brick In other articles I’ll show you how to burn out wax or PLA from plaster molds by using your microwave kiln I’ll also show you how to make your own crucible and how to melt metals in your microwave