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Gerhard Gerber

To foil or not to foil, that is the question.....

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Posted (edited)

I'm almost ashamed that I've had my kiln for over a month and it's never been used in anger.....

I was waiting for a manual since I was seemingly the only one out of a host of Southern African knife makers using this same piece of equipment to hold down the M-button and fiddle with the settings.... :wacko:

I found a manual and my brain finally kicked in and told me logic is still logic no matter where you use it.......devised a simple test to find out if the controller resets any changes when switched off.

Now my question, I bought foil as well, but I'm not sure when to use it.......I've seen it done so I'm also not looking forward to that process.

I believe for the 1095 and 5160 the foil is not necessary.

O1 and 52100?

Also, I plan on using 12C27 and 14C28 this year......?

Is my understanding correct that the foil is used (with the obligatory layer of newspaper) to prevent the carbon from being cooked out of the steel while being held at whatever temperature the steel requires?

Is this just to prevent scale and the subsequent hassle, or actually the decarb of the steel and effect on performance?

Edited by Gerhard

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It's a function of time at temperature.  Things that don't need a soak don't need foil because they're not it the heat long enough to cause major problems.  Things like 1095 can't be quenched fast enough to harden in foil either.

That said, the stainless steels require the stuff because of the scale and decarb that happens at the long high-temp soaks they need.  Plus you can plate-quench those two alloys still in the foil.  

For things like 52100 and 0-1 the foil is a pain, but does keep the scale and decarb off.  Antiscale compounds work just as well for these and (at least in the USA) are much cheaper than foil.

Finally, it doesn't have to be paper.  Some guys add a little oil, some add nothing at all.

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To expand just a touch further on Alan's post:  

The goal is to keep oxygen away from hot steel.  That is what the paper/oil/whatever is for in the foil packet; to burn up and use all the oxygen by the steel, and the foil keeps it there.  If you can eliminate the oxygen in the entire oven, that works too.  Just be aware that some gasses (inert or otherwise) do not play nicely with some electric heating elements and could cause pre-mature failure.  Though maybe it is worth it in some applications.  

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For most simple steels, foil is a waste, for things like 440C that need a long soak, they are a must. Scale on 440 is basically chromium oxide which eats abrasives like it is an abrasive- which in fact it is.

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Thanks for the replies everybody.

On 1/4/2019 at 2:56 PM, Alan Longmire said:

  Antiscale compounds work just as well for these and (at least in the USA) are much cheaper than foil.

Just recently saw a brilliant and well -respected knife maker in SA rave about some anti-scale compound as opposed to foil, but I have to take what I can get, the guy selling it is not a viable source for me due to the import duties etc etc....

I'm asking mostly for the O1, the blades I'll be HT'ing are very small, so if I have to foil and soak and go through the whole rigmarole for a 9cm blade it would be extremely inefficient....

The newest addition to my HT process is the vinegar soak, by minimizing scale using the pipe-in-forge method and the vinegar I can honestly say it's not a problem.

My concern is how much will I degrade the O1 during a 10 minute soak without protection?

@Joshua States will try white-out for sure.....

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8 hours ago, Gerhard said:

will try white-out for sure.....

I will be testing a DIY version soon and will post results in the original White-out thread.

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