Carbon Trapping?

[Biglou13]

The following are wood fired questions......

 

Is carbon trapping, the same as soot/ smoke trapping?

 

After all it is soot/smoke is carbon based. I have a some pieces that are almost all black on the outside.

Some body almost white with no black. Some withe black to flashy reds.

 

The particular clay body had approx 3% red art or 3% lizella , there remainding ingredients are porcelain and low iron ingredients. And the black is on most pots is directional. Hinting at trapping is not coming from body, but from fire. And then there are the pieces from same clay with little to no black (spots are from grog)? (Clay is much whiter than in pictures)

[Guest JBaymore]

More later.... pot on left... yowza!

 

Smoke / carbon...... yeah... that's the same.

 

best,

 

...................john

[Pres]

Don't know much about Carbon trapping even though I have used some carbon trap glazes. However, I'm sure the wood fire master will see your post.

 

Oh mentioning your post, I took the liberty of deleting your duplicate after reading both carefully.

[Marcia Selsor]

I agree with John, pot on left is a beauty!

Marcia

[Biglou13]

Ty sensei John, looking forward to it. I've red the piece on your site, But like most things you say it will take awhile for my brain to process.

 

Pres Ty must have double tapped submit. Ty for the compliments. I can remember a time not so long ago I was a woodfire virgin. Now I want to build my own kiln.

 

I'm super impressed with the color also... I had a few pieces that got the luck. My turn around time is 3-9 months on my woodfiring. Yet I'm still happy to get any done. I wish that flashing was on pots with my current skill level. I'm almost embarrassed by the form. The flashing is very much dependent on kiln. On last run not such fancy reds. If your interested recipe it is in making clay 101 post it's the modified 12D. By Odin maxwell who slightly modified the dick lehman recipe, who took notes from jack Troy.

[timbo_heff]

I thought carbon trap glazes are trapping the carbon from within and that smoke trapping is the lowfire trick of trapping carbon from the fuel source (?)

[Guest JBaymore]

Nope Timbo....... there is so little carbonaceous material in the average clay body that it is not really going to have all that much visible effect.  Screw up a body from reduced iron becoming a brittle low temperature flux on silica within the walls.... yes.... but doing much coloring on the exterior surface even under a glaze.... not really.

 

A clay body will "carbon trap" like in Lou's case even without a glaze on it in a wood kiln due to the (frequently) really poor mixing of fuel and air, and the high level of microscopic carbon particles floating about... combined with the volitiles from the wood ash (like potassium and sodium) that "fume" the surface of the clay...and perform much like the soda ash deposits on the surface of shino glazes.  The typical difference in an extended wood firing is that this deposition can happen for much longer periods in the wood kiln which can even include toward the cooling cycle side of things as embers burn off, surfaces are still fuming with volitiles, and airflow is cut off.

 

If you've ever saw Malcolm fire his serious carbon trap shinos..... the level of soot smoke coming off the kiln at really low temps was more akin to an anagama in reduction than the typical gas kiln firing most of us think of "in reduction".  Choo choo train stuff.

 

best,

 

.........................john

[Biglou13]

Why does some trapping happen in patterns like dots? And some just wash over piece.

 

What really gets me is in same firing I got a few pieces back that were virtually white. With. No trapping.

 

The recipe of above clay has large amount of neph Sy that fluxes early, I'm told since it glasses up earlier it's supposed traps earlier?

 

I was reading somewhere on the net where author stated that for trapping the kiln only needs to be in reduction at lower temperatures and it is possible to fire in oxidation after a certain point. ( looking for that article). Is this true?

[Guest JBaymore]

Yes Lou... that is true. And that is tr ue for ALL reduction glazes.

 

Have you ever thought about what color the typical iron bearing stoneware clay is? Brownish, right. Hum,...... but reduced iron oxide is black. So ... why is the clay brown, not black? It is because the instant the kiln is shut down, it is leaking AIR into the chamber. All of the surfaces of the clay and glaze are getting re-oxidized, even if they were reduced to start with.  So everything is getting re-oxidized anyway.

 

The KEY is knowing the maximum temperature (for a given clay body or glaze) at which reduction must have STARTED in order to cause the reduction effects you want.... and also the minimum temperature that the kiln can be returned to neutral or oxidizing conditions and still retain the effects you want. Every body and glaze will have this kind of range.

 

Optimum firing cycles fire in neutral atmosphere (stoichiometric combustion) at all times except when excess oxygen is necessary to oxidize some material, or in reduction when some material needs to be reduced. All other oxidation or reduction is wasting heat energy.

 

I've done studies of this for various glazes. For example, one celadon I have must have reduction begin before cone 04, and after cone 4 it does not matter what the kiln does. So neutral fire up to cone 06... reduce between 06 and cone 4 and neutral from 4 til 10. Save on heating up extra air and dumping it hot out of the kiln... and burn all the fuel in order to get heat energy out of it for most of the firing.... except for -10% between cone 06 and 4.

 

best,

 

.......................john