I found an old raku glaze in the back of my teacher's cabinet that he forgot about and said I could try it out. I don't know what its composed of since it just says, "red bronze raku" on the front. He has a kiln and a metal trash can for reduction. He has done raku's before, but not in a long time, so he can't remember how long to fire the pot for, although he guessed it could be four to five hours before you take it out of the kiln. I looked online and didn't find much right away, but one source said to start looking for the glowing orange color that signals its time to take it out after as short as one hour. I will only be in his class at certain times in the day, so I wanted to time the firing so I could be there to experience taking it out of the kiln. So, how long should a raku glaze be fired? Thanks, any help is appreciated.
How Long To Fire A Raku Glaze
Posted 15 March 2017 - 05:35 PM
We fire raku at school by watching the pot to see when the 'glaze' quits bubbling and becomes shiny.
this is about a hour from the cold start.
Posted 15 March 2017 - 06:56 PM
i have seen pots raku fired in 20 minutes once the fiber kiln is warmed up, another 20 minutes. so i think it depends on the kiln and if you have warmed up the bisqued pot.
you might take a look at some books about raku. steve branfman has some out there. raku seems to be more "by the seat of your pants" than by a clock.
Posted 16 March 2017 - 08:36 AM
Posted 16 March 2017 - 09:53 AM
From what I can recall of my Ceramics I class, we used a pyrometer and fired the raku kiln to about 1850F and got pretty consistent results. It took about 45 minutes from a cold start.
Posted 16 March 2017 - 10:14 AM
The kiln is started on high and takes approximately 1 hr. and 15 min.
When I use my wood kiln it only takes 30 to 45 min.
Posted 16 March 2017 - 04:00 PM
Well the short answer is "until its done". Raku is not so much about time as it is getting to the right temperature. Many raku glazes are formulated to fire to cone 06. One can peek in the kiln vent hole and see that the surfaces are all glossy and beyond the bubble stage. We have taken to using a little self standing cone 06 to get consistent results and I don't like peeking into the hot kiln any more than necessary.
Our raku kiln is pretty good sized to it can take as long as two hours to get to temperature. we run it fairly slowly until its past quartz inversion and then I was taught that you can blast it up. We have industrial natural gas so we never need to fully open the gas valve or it shoots flames out the top. We also raku kids stuff so take it slowly at first because some are sort of thick.
I have seen schedules that suggest temperature increases of 3 degrees per minute or something like that but I don't do that. Does your red bronze have a suggested firing temperature? We have one that goes to 06. Different kilns fire faster or slower than others. GL
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