Re-blue a mold?

[oldfart1956]

Fellers I thought I read somewhere here about re-blueing the inside of a mold after lapping it. I've lapped out a couple Lyman (steel) molds and it did appear they were blued before I started, so should I use a little touch-up blueing inside or just cast with it? Or is what I'm seeing (saw) just the results of heating? Many thanks in advance. Audie....the puzzled Oldfart.

[Horace]

Just cast it`s color will return.

Horace

[44man]

I don't think they use gun blue, just heat. The color will come back with casting.

[1Shirt]

Think I agree with 44Man from experiance.
1Shirt!

[hermans]

+1 on the not blueing the cavities, they will change color as the heat get's absorbed.

[fouronesix]

I'll be the odd man out here but yes you can reblue the cavities. It will not hurt a thing and can actually help in bullet release. Blue on iron (or steel) is simply an extremely thin layer of oxidation that provides a layer that resists lead adhesion. I clean the cavities with acetone or alcohol then apply some 44-40 cold blue with a Qtip.
Takes about 30 seconds so it's not big labor nor expense. Over time with use, the bare metal cavities will put on a thin layer of oxidation anyway. That even applies to brass and aluminum molds.

[oldfart1956]

Thanks folks. Mebbe just out of curiousity I'll blue just one cavity and see if it makes a difference? (have 3 molds lapped...double cavitiys) Audie...the Oldfart..

[williamwaco]

I have done with a propane torch.

BUT.

Casting is slower but does a better job.