Burning Smell When Firing

[cracked pot]

I'm doing a cone 04 glaze firing for the local art center as their kiln is temporarily out of commission and they need the work fired quickly.   My kiln is a vented L&L and I usually fire to cone 6.  There was such a horrendous burning smell coming out of the vent when he kiln reached about 600 degrees that I almost turned off the kiln.  I have never had this happen on any of my firings.  Then I remembered that the art center uses paraffin wax on the bottom of the pots.  The smell disappeared after the temp got up to 900 degrees.  Am I right in guessing that it was the wax creating the smell??  I'm keeping a close eye on the kiln but it looks fine.

[Min]

Yup, that stuff smells when burning off.

[Pres]

Wax vaporized at around 500-550F.  Smells goofy, but won't hurt the kiln, unless everything coated with wax, then you would have some oxidation on elements.

[cracked pot]

Thanks so much. I was afraid my good deed might bite me!

[Babs]

only bite you if you do it often and your studio isn't vented.

Gutsy firing hope your shelves are protected.

[cracked pot]

OK. Fired two loads for local art center empty bowls project as their kiln conked out and bowls needed to be fired ASAP.  

My question regarding paraffin burning off is this:  The art center fires in a small enclosed(no windows) kiln room with only a small exhaust fan in the wall.(No vent)  There is a drop ceiling in the room that connects to the rest of the building.  Burning odor in the building is strong when a firing is in progress.  Are the paraffin fumes dangerous?

Thanks.

[neilestrick]

OK. Fired two loads for local art center empty bowls project as their kiln conked out and bowls needed to be fired ASAP.  

My question regarding paraffin burning off is this:  The art center fires in a small enclosed(no windows) kiln room with only a small exhaust fan in the wall.(No vent)  There is a drop ceiling in the room that connects to the rest of the building.  Burning odor in the building is strong when a firing is in progress.  Are the paraffin fumes dangerous?

Thanks.

 

Paraffin wax is made from waste products from the petroleum industry. When it burns is emits soot containing several carcinogenic materials. Is it any worse than the cold wax most of us use? I don't know. Probably not. But I wouldn't run any indoor kiln without a vent due to all the stuff that burns out during a firing, regardless of the type of wax, and especially if it's getting out of the kiln room and into community spaces. It's a major liability issue for the art center. They need to have an HVAC guy put a fan of the appropriate size in the kiln room, or at least hook up a downdraft vent.

 

My reasons for not using paraffin wax:

1. Having a container of hot wax in the studio is dangerous. Major risk of a burn injury, or at the very least a big mess when someone knocks it over.

2. It stinks. Melted paraffin gives off vapors that smell up the room and ruin the air quality. The vapors can cause nausea in some people.

3. It tends to go on thicker, resulting in the heavy burnout you described above. Isn't there already enough crap burning out in our kilns without overloading it with wax?

[dave the potter]

Not to be critical but in interest of ceramic accuracy, organic material fired in an electric kiln  can cause reduction which can remove the oxidation layer on the elements and shorten the life of the elements

[neilestrick]

Not to be critical but in interest of ceramic accuracy, organic material fired in an electric kiln  can cause reduction which can remove the oxidation layer on the elements and shorten the life of the elements

 

True, but in the case of wax and such the shortening of element life is minimal. Very difficult to quantify, in fact.

[cracked pot]

Thanks Neil.  I will pass on your recommendations to the art center.  They do have a vent fan in the wall but apparently it died and no one noticed.  In the past, they have fired the kiln overnight when no one is around to monitor it.   There is a new director at the center now and she is trying to correct many deficiencies. 

Thanks again.

[Caroline]

^{I have a two large electric Skutt production kilns.  In the past three weeks, both have had indivual extreme events of black smoke pouring out of the lid and peep hole after two hours of heating...(Cone 5.)  Venting is a wall van that pulls air out, and cross ventilation in a large room. Because I was not there and had never experienced this in three years of use, I advised to shut the kiln off each time it happened.  THe result was badly blackend shelves, burned product bottoms, putrid smell...We had a Skutt serviceman come look and advised it was the Gulf wax buildup or residue which caused this and to only use wax resist or pottery approved wax for this purpose.  He advised after vaccuming everything, to fire an empty kiln to try to burn off the lingering wax residue that might have settled on elements and walls.  Since then I have been frantically searching if anyone had this problem and finally found these posts.  This past weekend we had another black smoking kiln.  The newly kiln washed shelves were all black as well as the bottoms of product and discs we set them on.  This again was after two hours of turning the kiln on and we had mixed the last of product that already had gulf wax and without, trying to start fresh when these were fired.  As I know the products were not damaged by smoke, which burned off with the next firing, I was going to do this again tomorrow, to save the product.  Could the wax be the only problem for the upsetting smoke and blackened product?  I am not doing any glaze, clay or routine differently, but since this is a recent problem that has now occurred three times, I am really worried.  I really need help to remedy this problem.}

[Pres]

I have been firing hot and cold wax in my kiln for years, never a problem, and never the extreme smokiness described here. I have a dedicated electric fry pan for the hot wax and heat it to liquid. On first dipped piece if too thick, I turn up the heat a bit, until the wax layer is thin and even with no white areas. These are carefully set aside allowing them to set before setting down. Mostly chalices and mugs done this way. Plates I do with cold wax. Larger pieces I sponge after glazing as with all other pieces. Kiln is in garage, firings are clean after 500-600F. I always fire slow to 1100F. then switch to high. In 30 years, I have changed elements 4 times, but then I only go through a ton every year or two.

[neilestrick]

If you've got that much smoke, it's odd that it's just from the wax. Wax does not build up from firing to firing. At the high temps that we fire it will burn out completely each time, so it shouldn't be any different now than it was before. Were there pieces in the kiln that had paper in them?