First time working with anything other than kingsford....so forgive the idiocy of this question, but I really don't know.

How do you tell the difference between "clinker" and unburnt coke?

Clinkers are fused debris and stuff that will "clink" when tapped with a metal fire tool like a rake and is heavier. Unburnt coke is light and will break up.

Clinker (in my forge) is usually a hard heavy substance that looks like there was some glass melted in to it. Different fires product different types of clinker due to the material that was not burned.

Sand, scale, rust, and impurities in the fuel all contribute to form clinker.

I had the same question when I started out and didn't have anyone to ask. So at the end of the day I let the fire sit as is and just go out. Then the next day I did a post mortem on the remains and learned what was coke, coal and clinker. In an ongoing fire, to me, the coke is rounded and the clinker is sharper/rougher looker.

Probably the most difficult thing for me to understand was the clinker thing ...the coal I use doesn't produce any clinkers unless I use flux in forge welding. After I finish a session of forging in the coal forge, I clean it out to make sure the fire is out, but there is never anything to take out such as clinkers. So, my conclusion is, I must be doing something different or I'm using some really good coal. Does everyone else always get clinkers in coal or what??

As per the title of my message - there is no such thing as a dumb question. If you don't know, or understand, or perhaps there has been a question raised about your understanding of a subject. You need to have an answer to clear up your question. Maybe others don't ask because they are too shy to ask or appear foolish or perhaps they thought they knew the answer.
Whatever the reason - it doesn't matter.
From the discussion thread that your posting is starting to generate, more people will end up understanding clicker than before you asked - me included.

Brian

Clinker is the unburnt inpurities from the coal
It heats up and usually liquifies and trickles down thru the fire where it comes in contact with the cold air from the blower source and resolidifies to form whats known as a clinker , sometimes referred to as dragon droppings

I usually use charcoal but when I use coal, I've noticed that when you let off the air, the clinker will generally darken faster than the coke or coal. And it looks sharper while the coke looks more like clouds.

Probably the most difficult thing for me to understand was the clinker thing ...the coal I use doesn't produce any clinkers unless I use flux in forge welding. After I finish a session of forging in the coal forge, I clean it out to make sure the fire is out, but there is never anything to take out such as clinkers. So, my conclusion is, I must be doing something different or I'm using some really good coal. Does everyone else always get clinkers in coal or what??

I forge with good quality processed coke and, like you, never get any clinker at all. In the days when you were allowed to burn coal in this country I used to get quite a bit of it.

The poor-grade anthricite that I use for heating the house produces a lot of clinker, but once it's cool it simply gets crushed up and goes out through the mechanical de-ashing system on the boiler.

So yes, a lot seems to depend on the fuel being burned.

With a bit of experience it's not that hard to spot clinker forming in the forge. It always forms in the same place, and shoving a cold steel poker through it will make it stick and pull out like so much toffee.



one_rod.

Charcoal is a very acceptable fuel for forging, however I would us "lump" charcoal not briquet charcoal.

Briquet charcoal has a lot of foreign material in it. Since raw charcoal is relatively expensive they add ground limestone which is cheap and a chemical compound to improve combustibility. I am sorry I don't remember the exact compound but I knew 20 years ago and if I remember correctly it is a chemical that we don't want near hot steel. My first reaction it contains sulfur but I am not certain.

You can see the limestone, as ash, remaining after the fire is out. Sometimes I have had briquets look nearly whole after they are burnt due to the quanity of limestone ash.

I have heard that coal dust, sawdust and clay are added to briquettes too.

Someone else had a good suggestion in that at the end of the day let your fire die down and out. Doesn't take too long once the air blower is shut off. Then dissect the fire with your clinker tongs (small very light weight tongs). The clinker will be towards the bottom, and has a hard feel to it through the tongs. Coke will have a softer feel to it. Coke is also very light when compared to the clinker, you will easily be able to tell the difference. The coal I am burning does not form too much in the way of clinkers, and usually mine are pretty small. If I have been forging for a few hours, I will notice a difference in the fire, it appears to die down and become less self sustaining. At this point, I shovel off the coke top 2/3 of the fire into the back of the pot. I then quickly scoop out the small clinker pieces at the base of the pot. Takes about a minute, and then I just push the still glowing coke back into the center of the pot and turn the air back on. The fire will pick up right where I left off usually in less than 2 minutes. Hope this was helpful.

Steve

I use coke to fire my forge. It does produce some clinker. I can tell that it needs to be cleaned out when I can't keep a good hot fire. I usually take a rod and run it to the bottom of the coke pot and push the clinker to the top so that I can remove it with tongs. The clinker has a obviously different appearance than the coke.

Jerry

How do you tell the difference between "clinker" and unburnt coke?

In my experience, coke is a matte grey substance, whilst clinker is shiny (and, in the case of the coal I am using now, smells strongly of sulfur.)

I've only used coke in English back-blast forges, and there the fire is normally hot enough to keep clinker melted. If you back the air off for a few minutes though, the clinker solidifies and you can hook it out in one lump using a right-angled poker. It's found just in front of the tuyere and feels very different from coke. Also I've found it sticking to the work when it's hot. Once you see it, you'll know it.

Since I had not smithed for about 2 years my youngest son doesn't remember dad beating on the anvil. The day after my first fire I went and dug through the cold fire bed and flipped the shiny almost bronze with streaks of blue and blacks colored clinkers out into the driveway. Well my 3 year old scooped them up and declared he found GOLD! Good ole mom now has 10 "gold" nuggets sitting on the nightstand by our bed.

So, I have now learned that a great way to determine if it is a clinker is if a three year old boy see's it at treasure.

James

Tell him it's Dragon Dung!

just a question my grandpa burns coal in the the shop to heat now when i scoop the ashes out they are like chunks of coke as he calls them now once i have a good fire going can i apply these to the forge for fuel??

Try it and let us know! There is no way for us to tell whether what you are describing is coke or clinker without a decent photo.

about every 2 hours i have to kill the air wait a couple minutes, take a poker and drag the clinker to the top of my fire, its grayish and ashy looking, I dump the hot ones in a steel bucket. There is so much sulfur in my clinker if it gets rained on it'll melt through the bottom of a paint can in 3 days,

oh

and my dog eats it when he finds it, he don't learn good I guess. I don'tt let him, he just does when he can......

Different coals produce different kinds of clinker. Some is more ashy than glassy.

For a while I had coal that would produce clinker that was kind of a thick
tar like when hot. You could take a small poker and pick the whole mass out and lay it on the ground. After a few moments it harded into a glassy donut.

I think that the glassy clinkers indicate a coal that is better for welding than the ashy kind. I was told, and it seemed to match my experience, that the ashy clinker tended to contaminate your weld surfaces .

Coke is light silvery black in color when broken and with a magnifying glass has very fine pores in it. The only coke that is heavy is petroleum coke, but when broken and examined with a 10x magnifier will have the same characteristics.

Industrial coke from the old steel mill coking ovens is pretty heavy in my opinion---a lot heavier than breeze made in the coal forge!

Industrial coke from the old steel mill coking ovens is pretty heavy in my opinion---a lot heavier than breeze made in the coal forge!

Guess it is all relative to one's experience. Pet coke certainly seems to me to be heavier that the bag coke that is sold today. I've never had occasion to handle blast furnace coke.

Pet Coke is produced all over the Southeren Louisiana and the Texas Oil Patch. From my own experience, and the experiece of others, it is so dense that it is not really usable in a coal forge. Burning require so strong air blast that you have too much oxygen in the fire. It goes out immediately when the blast stops. I've heard of methods to circumvent the problem but they don't seem very practial to me. (That is I haven't seen it personally)

I suspect, but have no literature to support, that it contains a lot of graphite along with the amorphous carbon.

I personally don't have much experience with using coal. For the silver work I do, the impurities in ANY type of coal contaminates the metal when it is molten. I have always used charcoal, supplemented with L.P. for a very fast fire. I guess it has to do with the trace metals contained in the coal. Not that I have any problem with coal... just the opposite, here in Sebastian county, the coal is supposed to be a very strong coaking type of bituminous. I can't wait to try some out on steel work in the future. I will let you all know...

Jim

the coke that I have access to is horrible dusty stuff that forms loads of clinker I have to keep on top of clearing the grate or I don't get any heat in the fire. The following morning my whole grate has a thick layer (often more than 10mm) of encrusted clinker all over it!

Sadly where I live we have two suppliers of smithing coke, both seem to be dusty and one is certaily more dusty (they also happen to be the cheaper of the two).