air hole in foil!?!

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I was just reading through the Allen Elishewitz's chapter in "Blade's guide to Making Knives" and am confused. He wraps his blade for HT in foil and then makes a hole in it to avoid a vacum. My understanding of this is that the vacum is the point or at least a lack of oxygen. Every time I have got a pinhole in foil I end up with a burnt blade. If he is making the hole because the steel is not stainless, why use the foil at all? Thanks for any clarification.
 
When using fiol, it's best to place a small hole in the foil
to allow for expanding gasses as the contents of the pack heat.

Not doing this will cause the foil pack 's seams to burst, and allow
oxygen to come in contact with the blade, causing decarburization.

Put a few square inches of brown paper in the fiol pack to absorb
the oxygen already in the pack. Seal it tight, then put a small hole
in the pack near the end of the tang.

After austenitization, you should get charred (black) paper out
of the pack. If you get ashes, that means all of the oxygen was not used up by the paper, and you may have a ruined blade.
 
Even if the ogygen is used up by the paper the hole will let more in wont it? I have never put a hole in my foil packets and only very ocasionaly get a pin hole in the packet. In those cases the blade is always burnt a bit by the hole to varying degrees. So is the point to create the hole in a place that will do the least dammage, like neer the tang? I dont understand how a hole in the packet will not allow more oxygen in after the paper has burned. What am I missing?
 
The paper really isn't supposed to burn.....just charr.

If it only charrs during the heat up, and soak, there will be carbon left to absorb the oxygen which is pulled in as the pack starts to cool.

The charred paper will use up the qxygen before it gets to the blade.

Putting the hole nearest the end of the tang will isolate any decarb to the
small area nearest the hole.

I use the paper that comes with grinding belts for this, and sometimes
will run a strip of paper all the way along both sides of the blade
and tang. That will minimise or eliminate that little bit of dacerb near the
hole, and won't hurt anything.
Depending on what steel you're using, your soak will be 5 to 30 minutes.
That's not long enough for your blade to absorb much carbon, at all.
 
Thank you Russ and R.J.

That makes sense to me Russ.

R.J. it's funny to hear such an acomplished maker doesnt do either of the things you hear you "must do". I also know you are a stickler for HT accuracy. I wish I had your kiln. :D

I will have to try both methods now, dang an excuse to make more knives, hehe.
 
I used to put some paper in the envelope to burn up oxygen, but the blades always came out with a hard, ugly skin on them. I stopped putting the paper in. No more "skin". The envelopes don't blow up like a balloon anymore either. :D
 
The paper will put a skin on the blade. I have had it happen too many times. Pure iron filling help, But use the correct foil. If you use the titanium foil sold by all the knife supply houses, for ATs, 154, etc, you will have a problem. The Ti-stainless foil, does a fantastic job. The Ti, burns, and robs the envelope of the oxygen. Which is exactly what you want. The problem is, that it is designed to work up to 1850 Deg. F. After that, it kills the atmosphere, and then sucks up against your blade. Many times welding its self to the blade. Not bad. But enough to cause problems with a thin edge. Makes it hard to get out of the envelope quickly for quench as well. go to MSC or Enco. They have a grade called high temp. It is good to 2200 Deg. F. It won't weld to your blade. The blades will be a touch darker than the . Ti-stainless, but there will be no carbon, and no shrinkage of the pack. Hope this helps. Oh! DO NOT PUT A HOLE IN THE ENVELOPE!!! This defeats the very purpose of using the envelope in the first place! But to a lesser degree. I'll strighten Allen E. out the next time I talk to him! Mike
 
Putting a hole in it defeats the purpose ! Squeeze out as much air as possible. Fold over double squeezing tightly . We never used paper but did use machining chips for items where we couldn't tightly form the foil around the piece.
 
me a tight pack and no hole or paper
i can show you how clean they come out when i do it that way
ooo and i plate quench too
 
The packet is designed to suck out the oxygen, putting something in it to burn out the air would just bring in more. Putting a hole in a packet would just allow air to come in. Not only is putting paper in a packet, or poking a hole in one not a "must do", it's actually better if you don't.
 
rj martin said:
I don't put anything in my packets, and I don't make a hole. Works fine for me.
Click to expand...


Same here RJ & BigJim. Tried the paper trick too and did not like the results. Now its a well sealed foil pack with nothing but the blade inside. They come out clean as a whistle :thumbup:
 
I put a small piece of paper in the pack, double seal the seams, but no pin hole. Works for me, so that's what I guess I'll stick with. This is the first time I've ever read about putting a pin hole in the foil pack. I plate quench all my air hardening steel while still in the pack also.
 
I used to use paper and stopped. The tiny bit of oxygen left in a sealed foil pouch can't decarb enought to even be measured. If I poke a hole in the foil when I'm wrapping, I'll wrap it again. No holes please.
 
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