I lit my brake drum forge for the first time in about 2 years this afternoon and had a problem with large clinkers. I was using charcoal that I had made when I was using the forge back then and I rarely had any clinkers then and on the rare occasion then they were the size of small pebbles. Today they were huge and constant. I wasn't thinking about them because I had not had this problem before. When my fire started acting weird I poked around and pulled out a clinker that covered almost the entire bottom of the firepot! Could this be because the charcoal was old and had possibly gotten damp from the high humidity we have during the summer here in Missouri?
Any advice or suggestions and thoughts are welcome.
Thanks, Jerry

i guess it could be all/none of those things but maybe the forge was mad because of not enough attention or the grimlins messing with you..but that is just a wasg......but seriously it might have been some moisture built up in the ash left in it let us know...jimmy

Two things cause clinkers. Non organic material: ie, dirt, sand, rocks. The other thing is melted metal in the form of scale or burned metal. Humidity, moisture, age have nothing to do with it. If you are getting clinker using charcoal there is either dirt in the fire or you are getting lots of scale due to an oxidizing fire. Too much air or the fire is not deep enough

Clinker is something other than burned fuel. I agree with Backwoods and suggest that about the 3rd fire the clinker will disappear. IF you have clean charcoal (no junk in the fuel) and run a deep fire with little oxygen getting to the metal you are going to forge, therefore little scale being formed, then I would suggest the clinker is coming from the rust on the inside of the brake drum. Two or three long hot fires should clean up the rust and the problem.

For those that have not experienced clinker, build a good hot fire and work some metal. Now throw a double handfull of dirt, scale, rust, small rocks, several nails, and anything else you normally would not want into the fire. Clinker forms and covers the air intake. All that junk will melt down and form a clinker you would be proud to show others. Now try to work the same metal and make a duplicate piece. Let the fire rest for a minute or so, and hook the clinker out of the fire, many times in one piece. Now try to work the same metal and make another duplicate piece. This will give you experience with a clean fire, working with a clinker, and working a fire with the clinker removed.

When the experiment if over, clean out the fire pot of all the fuel, ash, nails, rocks, dirt etc so the next fire you build is a clean fire.

Depending on where the charcoal has been sitting for the last two years, it may well have picked up enough dirt and other crud to be the source of the clinker. If so, you may solve your problem by washing the charcoal.

ron

I think that the problem was to much air, i am using a blow drier at the moment and I thought that it was a lot of air but kept going anyway. when I get back to the forge tonight I will leave the ash dump open to let some of the air out the bottom and see what hapens. The charcoal was stored in a plastic barrel to keep it clean and dry. Thanks to all and I will let you know what happens.

Some woods contain a goodly amount of silica in them naturally. Also if you are running your forge HOT like many electric blowers on a charcoal fueld forge you can get hot enough to vitrify the ashes (melt them into clinker)

Lit the fire last night, cut the air by about 3/4 still a lot of clinkers. Tom may be on to something I know that the wood around here has a lot of minerals in it, our bonfires are the most colorful that I have ever seen. I took a good look at one of the clinkers and they are more glassy looking than metallic. A whiteish bubbly material with some metallic in it. Guess I'll try to get my champion 400 set up and try some store bought lump and see how it works. I'll keep you all informed.

Clinker is not the end of the world, just something you need to keep on top of if you are having a problem with it. I get huge clinker out of my fires, ( too small of fire pot, too much air, too much burning up of the projects....) and I just need to stop every so often, let the fire settle and hook it out. Pulled out clickers the size of my fire pot!

As ThomasPowers said,

The impurities in the charcoal that were not cooked out at the lower temp, will solidify and give you the glazy lumps you get at the bottom of the forge after forging. Different charcoals will give you varied results of a similar nature.

That and that sometimes what looks like charcoal doesn't mean it is, I get a lot of small sandy rocks sometimes, depending on the batch

I fired the forge tonight with a different batch of charcoal and it behaved like it should, went through the old batch and found some rocks and dirt. Think I'll build a steel lined charcoal pit.

steel will rust==rust on charcoal==clinker in fire...again.

you can always line it with old brick that worked well on the last charcoal pit i had but that was about 10years ago just make sure to clean any loos mortar off the bricks (i got mine when we took down a chimney)

Old topic...but here is a picture of a clinker I fished out today from charcoal fire. The charcoal was scrounged from scrap burned in a fire pit. The wood only had a few staples and occasional broken off nail. Nonetheless between those and the ash & scale, the wood charcoal still formed a big donut clinker after about 3-4 hours of burn time.

Yes, a charcoal fire is more than hot enough to melt: dirt, sand, scrap metal, Orc fingernail clippings, etc. Clean your fire more often and it's not a problem.

Frosty The Lucky.

I've even found pieces of barbed wire in my charcoal.

Only clinker I ever found in my charcoal forge looked like tiny pea size pebbles 

Frosty, what, exactly, are you doing to get Orc toenail clippings in your forge fuel   What are som uses for Orc toenail clippings?  I can see maybe using them as a blade in a wood working plane or a chisel....

If you scatter them around the perimeter of your garden it helps keep Hobbits out of it!