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Joel OF

Coke spitting

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Hi folks, can anyone tell me why fresh coke spits? When I say spit I really mean spit, as in fires out fast and dangerous, today a piece hit me hard in the face!

It seems to be at its worst when I have a piece if metal in the brake drum and I add more fresh coke on top in the centre. I've found that placing coke at the edges to channel heat up through the middle is safest & keeps the coke lit well, but sometimes I find I need coke on top in the centre to reflect some back down onto thicker pieces of stock - and like I said, that's when it's at its worst. This seems to happen with and without the hair dryer blowing.

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Moisture in the coke will allow bits to spit, and although it may appear dry, if you have removed it from its plastic bag it has been delivered in, the condensation is absorbed in some of the coke pieces.

Heat + damp = rapid reaction to steam = splitting/detonation of coke lump

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Thanks for the quick reply. I have taken it out of the bag & put it into a large bucket, but i dont understand how that increases condesation? Surely the coke will sweat more in a plastic bag than in the fresh air?

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I'm a bit confused, I understand that it's moisture that's causing it to spit but I don't understand where you're saying the moisture is coming from and I don't understand if you're saying the bag is the best place for it or not...

Are you saying that if the coke is taken out of the bag then it absorbs moisture from the air? When you say "if you have removed it from its plastic bag it has been delivered in, the condensation is absorbed in some of the coke pieces." do you mean from damp in the air?

And in your last sentence "But it isn't going to dry out in a bucket if it is damp already." do you mean if the coke is damp already or the bucket is damp already? If you mean the coke is damp already then I'm completely confused because the only place it's been up till that point is in the bag.

I really want to understand this because yesterday was quite scary and ultimately very difficult to work with!

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"I'm a bit confused, I understand that it's moisture that's causing it to spit but I don't understand where you're saying the moisture is coming from and I don't understand if you're saying the bag is the best place for it or not..."


Water is an essential part of the commercial coking process prior to distribution, it then goes in large quantities to distributors who then bag it up ready to deliver to users.

Some companies screen the coke before bagging, others do not. So you may have damp coke being put into the bag at source even if it is screened

"Are you saying that if the coke is taken out of the bag then it absorbs moisture from the air?"

No, not unless it is kept where it can get wet,


"When you say "if you have removed it from its plastic bag it has been delivered in, the condensation is absorbed in some of the coke pieces." do you mean from damp in the air?"


The moisture is already in the coke, this is the source of the condensation.

"And in your last sentence "But it isn't going to dry out in a bucket if it is damp already." do you mean if the coke is damp already or the bucket is damp already? If you mean the coke is damp already then I'm completely confused because the only place it's been up till that point is in the bag."

Because it may start off damp when it is bagged, by placing it in a bucket, it does not mean that it will dry out any moisture, and you may even get some spitting from the coke even when it is dry, depending on the type of coke. You don't say what type of coke you are using or your supplier.

"I really want to understand this because yesterday was quite scary and ultimately very difficult to work with!"


I have tried to answer the questions individually in the quote above.


Basically this is a fire management problem, you are putting coke straight from the bag, or bucket on top of the fire, one reason you have a hearth with the firepot in is to allow you to work coke in from the sides to the centre, the coke on the side drying out from the heat from the fire before being raked into use. This minimises spitting unless it is a fuel type problem.

If you find it difficult to work with this may be another fire management and fire control problem and also a lack of experience, hair driers and brake drums also need air control systems and I would suggest you are using too much air, causing the coke to rapidly expand and explode.

Have fun and don't be scared, you are supposed to be in control, not the fire or the metal. Edited by John B

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Ahh brill, thanks for the detailed answer. I'm using coke singles, they're what a local blacksmith recommended & the company I got them from said it's what all the local farriers and smiths use. Yeah I'd discovered that it does it a lot less when I circle the coke around the edge and gradually rake it into the middle, but I hadn't put 2 and 2 together about the moisture.

Thanks again.

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Until it rotted through I stored a some of my coke in a perferated wooden and mesh trough next to my forge. I could get a couple or three bags of coke in it and I could pull out a shovelful at a time when needed. Made a difference to the amount of spitting and also to the amount of dust in the forge too. Trouble was that the trough rotted out after a couple of years and I haven't got around to fixing it, instead I farm the fuel better around the fire (of course having a large enough bed to do that helps)

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Ah nice idea. I have mine in half a beer keg which now thinking about it is a bad idea considering condensation. I'm actually using a brake disc for sake of the disc providing a bit of extra space to put coke on and rest work on. I've also set the brake disc into the top of an old oil drum (which I found in the remains of an old bonfire so I know any nasties have burnt off) so there's even more space to rest coke/work on.

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