Prepping crucibles?

Up until now I have been fabricating using a propane torch, just got my oxy-acetylene little torch and am trying to prep my crucibles and experiment with recycling my scrap but I can’t get the borax to stick it just scales off.
Thanks I’m advance

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You need to get the crucible very hot and try to evenly coat the inside surface with borax. I use a cheap salt shaker to do this…Rob


I do the same process as does Brother Rob. I have used Tea Ballers, small sugar sifters, and a piece of fine screen. What ever gets the borax on in an even coat.



i had similar results in the beginning…i yse a smith little torch oxy/ propane set up

try a bigger flame, and turning up the oxygen relative to the gas.

adjust oxygen slowly, observe the effect…

i think the crucible acts a a heat sink and takes a lot of heat to build up a sustained tempurature

just sone thoughts…



A couple people have mentioned using a bigger flame and getting the crucible really hot. Both are the keys to success. You need to get the crucible hot to the point that wherever the flame touches it turns red almost instantly. Depending on the size of the crucible and size of your flame, this can take a few minutes - I’ve never kept track but possibly 5 minutes or more.

Also, if this is a crucible for a spin caster, it’s critical you get the opening prepped as well. If it is, let me know and I can give you my approach for getting the opening prepped.

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“Also, if this is a crucible for a spin caster, it’s critical you get the opening prepped as well. If it is, let me know and I can give you my approach for getting the opening prepped.”

I for one would be interested to hear your approach.
Thanks in advance!

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Dave, here’s what I do to get the opening (the hole that the metal gets shot through) for a spin caster crucible glazed. I get an old tin or aluminum can and fill it with rocks. I prefer lava rocks but have also used driveway stone in a pinch. Put that on a fire brick or old ceramic tile. Then place the crucible opening end down on top of the rocks. Push the rocks around so the opening doesn’t have a rock up against it. Get your borax ready next. I put a “wad” of it in a little cup - have more in the cup than you think you need.

Then fire up the biggest torch you have with the biggest tip you have for it. I have an oxy/acetylene set up I use and, I believe, a number 2 tip. Get the whole crucible good and hot like I mention above then concentrate your flame in the area of the opening and get that area glowing red. Then I take the flame away, dump the borax over the opening quite unceremoniously, and immediately return the flame. Keep heating the area around the opening until the borax flows through the opening.

There can be some hardened glass (like stringers) on the outside of the opening that need to be cleaned off after it cools. Sometimes they just break off and sometimes I’ve used an old file to smooth them. I needed to redo the glaze the first time I did this because I was too careful with the flux. Now I just dump it on and let the torch blow it through.

Finally, do this outside or with lots of ventilation and keep your face back. Good luck!


I had really good luck coating the crucible when I mixed the borax with water to make a paste and then painted it evenly on the crucible.


My thanks to everyone for your advice. Thankfully after the holiday will give me a few days to play and I will try again.