Can’t glaze a crucible

I’ve tried map gas using Matt’s casting flux. Just made an ugly crusty mess that doesn’t look like glass at all.

Think I just ruined my second crucible. Tried borax like recommended by some and using a propane and oxygen set torch this time with a. Rose bud tip. All it did was turn my crucible a black mess. Not glasslike at all. I’ve watched a hundred videos. Nothings ever seems to go like in the videos.

Also is it normal for one of these oxygen tanks to run out after running for about 20 minutes?

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Just a thought…… I don’;t think you are able to get the “right form” of heat needed to do what you are trying to do. Your torch is far too small to heat “the entire crucible” at the same time, not enough total BTU’s to heat the ENTIRE crucible at the same time. You are only able to really heat a small part at a time and this is the problem. Also, the crucible walls are too thin to “hold” any heat you get into them and cool off far too fast. If I were fluxing a crucible with your outfit, it would be far smaller and much heavier. I think I see a “containment” to put the crucible in while heating it.(the apparent fire bricks behind the crucible) but this set up will NOT allow playing the heat source (flame) all over the crucible, just on the front and a bit on each side. Also, how big/forceful is the flame you are using? With an oxy/acyl rose but (about 2X times larger than in your photo) gas pressures are relatively high and the flame in roaring…… ESPECIALLY for a crucible of the apparent size you are trying to use. Again, thicker walled crucible I think would help some but you heat source is your problem……. Just too small for the size of the crucible

Hope this give you some thoughts or ideas. If more questions, I am sure you will get answers. See attached image for crucible that “might” work with your small rosebud tip (these are about 2.5/2.75 inches across the top X about 1.5/1.75 inches deep)
.Small Crucible Melting Metals Jewelry Making | eBay



The problem here is you are using the disposable tanks. They do not have high enough pressure to get the huge hot roaring flame you need. If you switch to standard size tanks with regulators you will have no problem. I do it all the time with the Smith Little Torch. Additionally your problem with the oxygen disposable tanks running out will be solved. (Two flame torches use much more oxygen than gas.). At around $10 per disposable oxygen tank you will quickly save enough to pay for the regulators for standard tanks. And best price is


Is it possible the black is coming from a highly reducing flame? Too reducing. A more oxidizing flame might clear the glaze?

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I don’t do lost wax, but I do cast ingots and other shapes with delft clay. The last time I prepared a crucible, I put borax into a salt shaker and that help control how it was applied to the very hot crucible. As suggested by others, it looks to me like you may not be getting it evenly hot enough. Good luck…Rob


Thanks for the tips. Are those crucibles for sale? They don’t appear to have a pour spout.

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Nice tip thanks! Just don’t want to mistake for salt.

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I use two different torches, a simple butane torch, Sievert style, which I use for soldering and, wait for it,… glacing crucibles, a spoonful of borax and a big bushy flame, jobs done!
it’s perfect for all purpose soldering, and I never get fire-scale,
but is not hot enough for smelting properly, for this I have an oxi-gas combi, same kind as yours, that I use exclusively for casting, as you noticed, the oxygen bottles have a very short duration. The butane torch on the other hand is on the same bottle since 4 years. :smiley:

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It is kind of a learning process when figuring out how to properly glaze your crucibles. I’ve used my little torch for it, even without a rosebud tip.
But after some experience and learning with practice is, I always use my bernzomatic Ts8000 with either propane or mapp gas. It’s a bigger torch used for lots of applications but I love it for glazing crucibles and soldering big silver pieces and annealing big pieces.

What I do is get enough borax in the crucible so that some of it sticks, and keep the heat on it with my big torch and swirl the crucible around so that the borax swirls around the inner parts of the crucible.
You could do the same with a big butane torch, but it must be a bigger one.

My first though at reading your post was what another poster though, maybe your flame does not have enough oxygen in it. Make sure you’re getting your flame enough oxygen otherwise it will turn things black, similar to what your crucible looks like after first tries.
I don’t think your crucibles are ruined either, you could re-try them both with borax and the way I do, wouldn’t hurt to try!
Good luck :+1: :blush:

Also, Andrew Berry has a couple great videos on preparing a new crucible on his YouTube channel At The Bench.

With love
Erin Edwards


Yes. The ratio of oxygen to fuel is quite high. After going through my first five disposables lickety-split at $10 a pop, I invested in a larger oxygen tank and regulator. :smiley:


These tips are all awesome. I’ve been really struggling with glazing my first crucible as well, but I see now that I’m probably not getting it hot enough. It begs the question though…can you buy PRE-GLAZED crucibles anywhere? I looked online but didn’t see anything.

Google Craig Dabler, he has a FaceBook group and a website that revolves around sand casting. He sells pre-glazed crucibles and has a video accessible from his website where he demonstrates how to glaze your own crucible. His website is called DIY Casting.

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Thank you!!

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I had that problem, black crucibles, when i tried to use a small hoke torch to glaze. now i use an acetylene torch

FYI I use borax paste in order to get an even coat on the crucible . just mix with water and spread it around.