I fire-blued lock retaining screws and a top jar screw last night. I got the first one pretty well, but must have over heated the second one. I buffed it out and tried again. Apparently the change from straw to blue goes pretty fast. Maybe I need to move the heat farther away. Any suggestions to help out?
Another question: Do you do anything to protect the bluing, like a coating of wax
Thanks.
Regards,
Pletch
Propane torch, heat the shank of the screw and let the heat flow to the head. As the color comes right quench.
If it needs blue on each end heat the middle.
It takes practice.
If you want to get really high tech make a small tank, I used a piece of conduit with the zinc burnt or pickled off, welded ends on it and holes for heavy wire to hang it from for longer pieces like mainsprings and a stainless soup ladle for smaller parts, fill with potassium nitrate and heat till it melts, 700 degrees or so. Immerse the part to be blued. As the coating melts off the color will start to come. Its often necessary to immerse the big end first since it heats slower. This is the best way to do larger parts.
According to the Madis book Winchester blued barrels with PN with some manganese dioxide in it. When the proper color is reached to part is removed and when clean and cool it is coated with oil and the oil baked off.
I have tried this and it does make a darker blue that is a little more durable. But the color is not the fire blue anymore. Heavier oil makes darker color. It can be used to blue parts that need to match the typical blue found on modern guns to "fix" a screw etc that needs color to match.
The Manganese makes the molten PN darker and its harder to judge the color. I tend to use straight PN though my one "tank" still has the oxide in it.
PN should be available on the WWW and Brownells sells it in buckets.
The PN "evaporates" into oxygen so it goes away in use and needs a refill now and then. When using this process it is best to get all the parts to be blued ready and do them in a batch.
Some PN will adhere to the part but it dissolves in water.
I don't know of anything other than the lacquer used to coat color casehardening that will protect the color.
This process is good for tempering springs BTW. Residue washes right off leaving a nice blue, clean spring. I let these air cool and wash the spring later to remove the remaining PN.
I think this process make a *somewhat* more durable coating.
Dan