HT packet

[Pelagicfun]

Probably a simple answer but Google didn't find it for me. I just had a foil packet come out like a balloon for the first time. What could have caused this?
Thanks
CC

 

[Stacy E. Apelt - Bladesmith]

This is a good and a bad thing. The good is that the packet was so tightly sealed vapors could not escape.

The bad was too much volatile material. Paper, WD-40, moisture on the blade. oil, etc. All will vaporize and blow up a tightly sealed packet. I don't put anything on the blade or in the packet. Also, make sure you flatten the packet and don't trap too much air.

 

[JTknives]

I find at high temps just some trapped cold air will inflate it. If you consider the expansion ratio of air pv=nrt. At a start temp of 65° the air(nitrogen) once heated to 2000° Would be at 120psi if the packet did not expand. 120psi/14psi= Is a expansion ratio of 8.6x that starting volume. So it does not take a lot of air in the packet to expand to the point that it’s puffed out.

 

[Pelagicfun]

Ahha. I didn't heat up my shop yesterday because I just ran out to do a couple blades. It was snowing so it was probably 30 or so out. I let the blades sit on my bench while the oven heated up. First time I have done this. This is likely the cause? I'm sure they were clean. I used acetone to get sharpie off before wrapping. They seemed to come out just fine.

Thanks guys
Clayton

 

[Ken H>]

One advantage of the puffed up package - no SS foil is sticking to the metal {g}