Is scale finite?

[Mark Barone]

I messed up hardening a blade. I didn’t have enough oil. I cleaned of the scale and reheat treated,So I started again. I noticed the second Time when I dipped in oil there wasn’t much scale? Is that because it all came out the first time? Does that affect heat treating?

 

[Chris Railey]

In very general terms, what is commonly called scale is actually oxidation where air meets the hot steel. My guess would be in the first quench part of your hot steel was still exposed to the air, hence more scale. In the second quench you had enough oil to cover the entire blade hence less exposure to air and less scale. If using a forge you may need to adjust your flame to keep scale down as much as you can.