Saturday, September 28, 2013

How I Use the Coal Fire

I’ve used a number of coal forges but now I only use the side draft one inside my studio.  I’ve used the great bellows, the spiral gear hand crank fan blower and the several lever powered blowers of the same fan design.  They all work and have advantages and disadvantages.

I’m no longer in the business of doing shows so I’m just interested in effeceint use.  When I built my currently forge I placed a Champion electric blower outside the building on the porch to keep the noise level down inside and plumbed a nearly silent hand crank blower on the other side right next tot he forge pan.

In everyday use I use the electric blower turned down well below it’s maximum speed and rarely use the hand crank blower at all.  The tuyere is plumbed from both sides, electric and hand crank.  On the hand crank side there is a sliding blast gate.  On the electric side there is a hand wheel screw valve to further choke the maximum airflow.

In our normal work cycle the forge work is well organized and laid out so we go from one item to the next non-stop for two hours.  We discuss how the work will proceed and in the couple of hours we forge there is very little conversation.  Incidentally in the image “Hand Crank Blower” a can of black spray paint can be seen. We use the forge hood to make drawing in soapstone when needed and use the black spray paint as the eraser.

The electric blower runs essentially all the time maintaing a large hot fire.  The intensity of the fire is controlled almost exclusively with the blast gate on the hand crank side.  The only time the blower gets turned off is when we shift to a new project and have to get the new tools and workpieces arranged and when we quit.  Ken packs the fire, turns off the blower and allows a bit off cooling before raking out the fire pot.  This leaves plenty of coke ready for the next day and the clinker is in one solid ring, easy to separate from the coke.

I’ve worked with forges which require flipping the the blower motor switch off when a heat has been taken so that excessive fuel burn is avoided.  The disadvantage is that the heat falls off and to take another heat the blower must be restarted and the heat driven back up.  If the work being done requires some thinking between heats or if the smith is demonstrating and talking the additional time may actually be desirable.  However, if the work is a production run and there are multiple pieces being worked, it is a disadvantage.  Moreover, in my situation where Ken and I are alternating fire tending and forging with every other piece it would be a big waste of time.  We strive to bring each piece out at a orange/yellow high forging heat temperature unless lower world be better.

I didn’t learn to work the fire that way and that’s not what I teach when I have the opportunity but it is the way I do it now.  It’s probably always best to learn a craft the tradition way and modify the techniques so they fit the specific requirements of the shop later.

In a normal two-hour work run we don’t remove clinker until the fire is torn apart when we quit but we do turn the clinker breaker frequently and empty the ash dump a couple of times.  About the only time the quench can gets used is to put out any smoking coal after the fire has been pulled apart with the rake.

I don’t use wet coal on an everyday basis but I probably would if I was doing a lot of forge welding.  Also, a straight poker is the only tool I use to actually control the fire.

Take another heat.

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