Ok,I want to give a summary of what I understand to check if it is correct.
1. The "clean up" is another term for soaking.
2. A soak is a time of oxidation before the kilh is shut
3. A soak would hrlp if I want to "soften" the reduction in order to give surface oxidation to thin glaze areas or edges of clay.
4. A soak would help my glaze/clay body if I had larger particle size in my glaze/clay. For example, if I want to add pebbles of granite to my clay body, I may need to soak to allow the pebbles to melt.
5. A soak can help hide/correct my uneven firing technique, allowing the kiln to equally redistribute its heat.
6. If I don't need any of the above, I don't need a soak.
7. And finally, if a soak of 2 hours is needed in a big kiln, it is also heeded for the same time in a small kiln.
Is that right? Do I have it yet?
Now a question.....When and why is a preheat used?
#1 - Yes... sort of. "Clean Up" means whatever the speaker/writer thinks it means. Some might consider it to be a soak held in in oxidation.
#2 - No. A soak can be in oxidation, neutral, or reduction atmosphere. A "soak" is just a holding period at about the same temperature -only slight variation if any. (The heatwork is still increasing.)
3# - No. Unless you have a very special (and unusual) kiln..... the kiln is going into oxidation (if it was not already there) the instant you cut off any possible fuel source. Unless you alter it, it stays in oxidation throuighout the cooling cycle. The surfaces of ALL glazes will typically be oxidized (that is why "reduction fired" stoneware looks brown.... the surface is re-oxidized).
#4 - Yes. This gives the time for heatwork to accumulate and time for chemical reactions to complete. You can often have a similar effect by firing to a higher cone (more heatwork).....but not always. Sometimes large rocks take a LOT of heatwork to melt.
#5 - Yes. Basic law of thermodynamics...... heat energy ALWAYS flows from areas of higher concentration to areas of lower concentration. (Water does not flow uphill.) If heat energy input and heat losses are stabilized (soak), then the hot parts will get cooler as the energy moves to the cooler parts, and they then get hotter. (Temperature is the result of the application of heat energy to a substance.)
#6 - Yes.
#7 - Yes.... IF that soak is needed for something other than evening out the thermal lag or unevenness in the big kiln.
A lot of the terms that potters use are NOT "legally" defined nor universally understood. So "preheat" could mean most anything. For some it means lighting a pilot burner on a sealed load of ware and running it overnight. For some it means turning on the bottom bank of elements on an electric kiln overnight with the lid mostly open. For some it means burning a wood fire in the damp kiln to dry it out before loading the wares. Generally it means a very low and slow application of heat energy in the kiln. Only typically needed if the kiln is wet or if the wares are wet. Can waster HUGE amounts of energy. Often is done totally unnecessarily.
Professor of Ceramics; New Hampshire Insitute of Art
Guest Professor, Wuxi Institute of Arts and Science, Yixing, China
Former President and Past President; Potters Council