Why do some coins get brass streaks...

[casata137ec]

...and what can be done about it? I use a brass/pin scraper setup in a double sided pin vice (I am using hobby grade rod stock for my pins, cut down and sharpened) and a standard fine bristled brass brush for my manual brass tools, and on most coins it is fine, but on some I can barely touch them and there is a brass streak on the surface of the patina (literally, not the coppery look of rubbed off patina, but a translucent goldy/brassy sort of color). Anyway, how do I avoid this (well, I can figure that out), and how do I get the brass leavings off?


Thanks

Chris

[awl]

Can you post a picture?

[casata137ec]

Crud, soon as I run in to one again, I usually just toss them back in the pot. (thanks for all your responses btw awl)


Chris

[bruce61813]

what you are seeing is probably the brass coming of your pin. It is softer than the material you are trying to clean, so it comes off. I know in metal working the sometimes use "pencils" made of aluminum for the same reason, it marks easily and is just as easy to rub off.

Bruce

[casata137ec]

Bruce, that's what I was thinking, but I wanted to be sure that it wasn't some sort of reaction that I didn't know about yet, it does seem that if you throw them back in #1 for a day or so that it brushes off with a nylon brush. (probably particles that get embedded in the clay)

Chris

[bruce61813]

Very often you can wipe of buff it off right away.

There is a technique among metal workers called brassing. You heat the work piece you to high red and rug it with a brass brush. the brass wil stick to the hot surface, so when the item is cool, there is a brass layer. Generally the piece that is being worked is iron or steel. Sometimes copper is used instead of brass.

Bruce

[SC]

For removing the brass streaks I try rthe following steps, stopping when it works: rubbing with finger, then nylon brush, then nylon dremel, the fibreglass brush.  Do all when coin is wet.  Never had marks I can't get off.

Because, as Bruce says, it is a sign that the brass pin is softer than the material, brass streaks can be a sign it is time to change to a harder pick.

Shawn
 

[casata137ec]

All good advice, thanks.


Chris