bricks on RMH chamber's have phosphorus smell

Hello all!

The stove is working great so far, no cob over the benches still (hope I'll be able to do it on tuesday) but draft is strong and is really easy to start the fire. Today it's really cold here so I've been firing it for some 4 hours, after that, burn chamber zone began smelling somehow like gunpowder, or phosphorus kinda odour! Does anyone knows what could be the cause?

I do suppose it could be because one or more of these reasons:

1- wood ash mixed with the clay slip I've used for insulating pad under burn chamber getting hot

2 - clay slip used for bricks laying (or phosphorus content on it) getting burnt under high temperatures

3 - firebrick or perlite themself (that seems not a clever one since they came "fired" yet)

Any suggestions? it's not funny to have such odour, makes me nervous about maybe having some serious and dangerous problem with the stove...

Thank you in advance:

Manuel

Volcanic island?

Volcanic island?

hahaha, nope

Anny other suggestion??

I've been searching for simmilar post and questions but couldn't found anything about this smelly heaters.

Jose Manuel Bonilla : Since you say your fire is doing well, and things seem Rocket-y, I think every thing is fine, I too wonder out of
what materials the brick were made, could they have been coal fired, or used? As long as you tell me they are lightweight bricks I Think
you will be happy - your bricks very a lot from ours, IF I remember the pictures you posted ! Good Luck ! Via con dios ! Big AL

In all my years as a chemist, this is the first time I've heard the phrase "phosphorus smell". Do you mean it smells like burnt matches? Or firecrackers that just went off?

Most of that type of odor can be ascribed to SO2, as there are various sulfur compounds used in gunpowders and matches. A lot of things, on their first firing will offgas strange smelling fumes. Generally, repeated firing cycles will reduce the amount of these compounds until there is no residue to cause the odor. If it really bothers you, take it outside to air it out. If it's not really movable, blow air through it and vent it to the outside.

In all my years as a chemist, this is the first time I've heard the phrase "phosphorus smell". Do you mean it smells like burnt matches? Or firecrackers that just went off?

I'm sorry, I'm not so good at english writing neither at chemist so I didn't explain good enough. I said "phosphorus" because we here use the same word for "matches" and I thought it was because they should be made of that...

Most of that type of odor can be ascribed to SO2, as there are various sulfur compounds used in gunpowders and matches. A lot of things, on their first firing will offgas strange smelling fumes. Generally, repeated firing cycles will reduce the amount of these compounds until there is no residue to cause the odor. If it really bothers you, take it outside to air it out. If it's not really movable, blow air through it and vent it to the outside.

It's more like firecrakers. I've asked the ceramist friends about it, they've asked a friend who knows about soil composition nearby... and they think it's because of the iron (among others) sulphide that happens to be on these clays.

I'll keep firing it and hoping it will dessapear as soon as everything burns oot and the clay get dry. I'll let you know how it goes.

Yesterday we cob-covered the flues of a complete bench and half another. Tomorrow I hope we could built the column. So far so good.

Thank yoo for your answers.

iron (among others) sulphide that happens to be on these clays

Ah-ha, now we're getting somewhere. What may take care of that would be pre-washing the clay with hydrochloric acid (regular pool acid will do) before you use it. If you can pour acid on the dry clay and it smells of sulfur, then you know you are on the right track. Hydrochloric acid will convert the iron sulfides to iron chlorides and the sulfide makes H2S which is volatile and goes away. You want to do this outdoors though, H2S is toxic so you don't want to be generating it in an enclosed space.

Thank you very much, John.

Today we'll have to mix some more batches of cob to finish the second bench and begin with the column. I do think I have some hidrocloric acid at home so I'll be able to test the clay.

But we have put lots of cob yet, and the "J" is really covered with it (I've used clay slip to stack the bricks and hold the perlite insulation) and it would be a pain to have to take it all out now (winter is here and we're in a hurry if we want to have nice warm benches for the new year). So what I would like to know is wether the sulphur inside the clay would estabilize somehow and stop going out into the air with the repeated firings... hope so!

Soon I'll post some photos of the ongoing benches.

Have a nice day!

Manuel

Jose Manuel Bonilla wrote: So what I would like to know is wether the sulphur inside the clay would estabilize somehow and stop going out into the air with the repeated firings... hope so!

Manuel

Yes. Over time, any sulfides will oxidize and go up the stack as SO2. Any sulfates (SO4) that are in the clay minerals are stable and will most likely stay there through repeated firings. It shouldn't take too many firings for it to stabilize out.