Terminology, Purpose and Process

[LeeU]

Anyone want to take a try at posting a compressed and simple (just a few sentences each) description of the differences among: soak; hold; candling; preheat?  I saw a good explanation of the correct use of the terms and their respective applications on another site but now can't find it. I like that it was all in one place and wanted to save it into my Terms and Tips file. 

[Rebekah Krieger]

Hmm - my "off the hip" reply will be 

soak/hold is done at the peak of firing when kiln has reached target temperature/cone level to ensure all glaze materials have had their opportunity to mature and develop. 

 

Preheat/ candle is done in a bisque firing prior to the kiln rising temps above 200 to ensure all moisture has left the pots. This is done to prevent internal moisture from boiling and exploding your pots. Candling should not be done in place of verifying a pot is bone dry. It should be used only as added insurance. 

[Min]

This is what I take those terms to mean.

Soak: keeping the kiln at any given temperature for a set length of time. Example: at the top end of the firing, holding the kiln at the final temperature to mature the glazes/clay. Can soak at any temp going up or down.

Hold: I take this as pretty much the same as a soak. Can hold at any temp, example would be crystalline glazes needing an extended hold on the temp as the temperature declines. On single thermocouple kilns or manual kilns a hold or soak helps even out the temperature in the kiln.

Candling: Warming the kiln and pots slowly and keeping it a low temp to thoroughly dry the clay.  I’m guessing this term came from combustion fired kilns and there literally was a flame.

Preheat: Warming the pots up but not necessarily holding the temp as with a candling. Example would be when raku pots are put on top of the hot kiln to get them warmed up a bit prior to firing.

[Marcia Selsor]

My interpretation

soak; keeping the temperature level to even out a glaze....or during a body reduction from 09 to 04, or a glaze reduction. Soaking can also be used in Soda firings when adding charges of soda. then there is a soaking when trying to brighten iron glazes in electric kilns in a ^6 firing. This is done a t ^6 for maybe 20 minutes and then the temperature is dropped tp about 1960 and held for 20 minutes to 2 hours depending on personal preference. I soak my sagger firings for 20 minutes to assure complete combustion of material in the saggers.

hold: somewhat the same. sometimes. Crystalline glazes use holding at the same temperature to grow the crystals, but soaking could be the same definition

candling: I use this more for gas firings.. candle overnight or at the beginning of the firing to slowly warm up the chamber and the stack or chimney. That makes the chimney draw the heat.

preheat: warming up the kiln to drive out the moisture before hitting 212 where steam can blow up work.

Marcia

[Pres]

23 hours ago, Rebekah Krieger said:

Hmm - my "off the hip" reply will be 

soak/hold is done at the peak of firing when kiln has reached target temperature/cone level to ensure all glaze materials have had their opportunity to mature and develop. 

 

Preheat/ candle is done in a bisque firing prior to the kiln rising temps above 200 to ensure all moisture has left the pots. This is done to prevent internal moisture from boiling and exploding your pots. Candling should not be done in place of verifying a pot is bone dry. It should be used only as added insurance. 

Preheat and candle. I consider these to be both the same, using them to remove the atmospheric water from the kiln, propped lid or even in my case, no lid or lid off kilter. This last kiln load was more of an overnight with 2 switches of the L&L on 10%.  and then a lid on, with no peep, at 30% for 4hrs, 50% for 4 (dull red heat), then fired to ^06  in another 6 hrs.. This because of the two pickling crocks in the kiln that are thicker than usual, and larger than usual. One a 25# and the other 20#. I had the load also packed with chalices, apple bakers and mugs. Unloaded the kiln on Monday with not a single crack.

 

Glaze firing for me is to ^6 electric, and I fire manually, when cone 5 goes down, I back down the each switch to 90% watching the movement of 5&6, If 6 is dropping too fast, I back it down a little more watching til ^6 has dropped to 1/2 way down sticking out, but not curling down. Then I turn down to 50% until ^6 goes to touch base, ^7 is just about pointing to 2 o'clock. Then I turn all but the bottom off, with the bottom at 10% to slow cooling further. However, I now have a much thicker lid, and lid fit so this makes cool down slower, so the bottom switch goes off about 4 hrs. later. So I really think I do soak and hold, but very carefully and very controlled having fired this kiln in that way since the early 80's.

 

best,

Pres