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I am working with Laguna B mix stoneware, bisque firing at cone 04 and glaze firing at cone 5.   I use Columbus Clay wax resist on the bottoms of each piece and often in resist design between layers of glaze. Sometimes I will get wax resist on an unintended area of bisque ware and want to remove it.  I ususally just put that piece back in the kiln with my next bisque firing at cone 04 and the wax burns off.  Any other suggestions to remove the unwanted wax? At what temperature does the wax burn off?  If I had several pieces could I fire them at cone 022?  or even lower? I ask because, (in a brainless moment) I waxed the bottoms of several pieces before signing them with underglaze as a usually do.  

 

 

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Small areas of unintended resist can sometimes be sanded off depending on the piece.  For these pieces could you maybe scratch through the wax and then apply underglaze on the scratches.  This works so nicely when the clay is still moist, I have no idea if it would work once the piece is bone dry.  Maybe rehydrate the entire piece slightly?  Just brainstorming here....

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I have tried a half dozen different methods of removing wax, and the only one that I have ever been satisfied with is burning it off in the kiln. Every other method has left a noticeable spot. Wax will start burning off at around 500F degrees, but I would go up to 800F or more to be sure.

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you can always sign the bottom with a sharpie after the piece is finished and glazed.  if you have a self cleaning oven it goes to about 800 degrees. never tried it, though.

 

this is another advantage, (to me) of single firing.  i can carefully lift off hot wax with a knife edge and lightly sponge the spot if needed.

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I can usualy get the wax off by scraping with the edge of a metal rib, you know the one that come in every beginner kit.  Make sure you scrape deep enough to get all the wax which will mean you are digging some of teh clay body away as well.  I have never burnt it off, but I am sure that is a good route as well, just costs for time and $$.

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Have you tried heating the resist with a hot air gun or a propane torch? I haven't tried it, but it seems it would work. Maybe setting it on top of a hot wood stove?

 

I like the idea of using my self-clean oven, the oven would get clean, too, and how often do I remember to actually do that?

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I have tried using a simple candle lighter, to burn off the resist.  Doesn't really work, and leaves soot behind.

 

Like Neil, the only surefire way I've found is to just refire them in a bisque, or other such low firing.

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I have sanded it and finished buy rubbing with another bisqued piece which embedes the dust with some luck-I have tourced it off but you need to be carefull as you can crack a piece with uneven heating-a hot kiln will burn it off or for 100% sure fire re-bisque.

I have also groud it off on a bench grinder thaen sanded but you can mess your work up.Rubbing Alcohol will also cut most waxes.

Mark

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The wax will burn above 500F, but the soot will remain until about 1000F is reached.  I had an opportunity to prove it. :)

So, in order to burn out wax resist off bisque stoneware and prepare its surface for glazing,  I programmed my small kiln to run to 1050F at 600F/hr ramp rate, hold it there for 15 min, and turn off.  I avoided all the potential problems of quartz inversion by keeping the max temperature just below the inversion point, yet high enough to almost completely eliminate the soot.

P.S. My small kiln is capable of reaching 1000F at 30 min, but I felt uncomfortable to go that fast.  Maybe, I shouldn't be afraid...  I wonder if anybody ever tried 2000F/hr ramp with bisque stoneware (not greenware!) to just below the quartz inversion point.

Wait, when I think about it, this ramp rate happens very often when I do raku/saggar firing... Moreover, I go well above the quartz inversion. H-mmm.  I guess the next time when I need to burn out wax, I'll let the kiln go as fast as it can, and will have the result in half an hour vs. hour and a half (plus cooling time, of course). 

I'd, probably, slow down a bit at the quartz inversion point (by adding a 500-600F/hr ramp from 1000F to 1100F to be safe) and then continue raising  the temperature at full speed to 1200-1300F with, maybe 5 min of soaking. This should eliminate thick soot more reliably.

Edited by MichaelP

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I think quartz inversion is only a big problem if there is an excess of silica in the recipe, I think raku clays and such don't have much.  Porcelain can have a large excess so it's more sensitive to that quartz inversion change.  

I'm probably wrong but I remember reading that somewheres

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I'm currently using a solder pencil.  It's butane and puts out a really small bright flame.  The soot doesn't seem to be a problem to glaze over.  You do have to be careful or you'll pop a piece out of the bisque.  I wax a lot, somewhere around a pint per kiln load.  Drops where they shouldn't be are inevitable.  

 

3in1-MIni-Gas-Butane-Torch-Solder-Pen-Iron-Gun-Welding-Cordless

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I tried larger flame (weed killer) a couple of times before, but even with careful preheating of the whole piece, it always fractured. I will try my mini torch on small wax spots again.

Thank you.

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I think the the best method is not to get wax where you do not want it.

If its dripping its to thin. I use a sponge and wring out any excess to control really is key.

The way you hold pots so drips fall aways is a good habit if your are a slob with drips.

One hand for wax one hand for wares is also a key point.

You learn a lot but doing huge volumes of wares and how to keep mistakes from happening in the 1st place

Now if you do get some on a spot there are a few tricks.

1st is keep a wet (water) sponge next too yoiu so you can wipe it up immediacy or sooner before it drys-this is about 90% effective

second is to sand the spot with sandpaper or even use a dremil tool to grind a bit of bisque off

third you can rub the spot with another broken picece of same clay body thats bisqued to get the particles teh same so glaze sticks well-this is a tricky deal as to must dust makes it crawl more.

4th burn it off with a hand torch but you need to know not to hold it there to long as that will crack the ware tso this my friens is a learned skill but works really well -not to much heat and spread it out over an larger area. I work with porcelain which is not forgiving like stonewares.

I like to do a combo of some of the above items .

I gave up rebisquing 40 years ago as a waste of everything as these tecniques work just as well.

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