I have had some brass that I purchased new back in the 60’s and 70’s. I had big plans back then. These engines were packaged in their original boxes about 20 years ago and put in storage. I have opened them up recently and found that some of the foam has deteriorated and stuck to the brass. I have been able to brush most of it off, but the brass is a bit discolored where the foam stuck to it. Is there any way to remove that discoloration? Also, one of the engines has some greenish blue crystals forming on the boiler front. Does anyone know what kind of reaction took place and what solvent to use to remove the crystals? Thank you for any help you can offer.
This subject (foam + brass) has been kicked around over the years on the forums. You might do a search on this one and/or the Atlas one. My general impression is that if/when you want to paint them, you wash off the foam bits with an appropriate solvent. If you want shiny brass instead, it’s strip off any clear paint, polish, and re-paint (might as well just paint the critters in color).
Now, those blue crystals, that’s new. I think. The color sounds like there’s a copper salt there, probably from the brass. I would guess that someone didn’t clean some flux off properly. My guess would be to mechanically clean it off, and then apply the appropriate solvent. Which one? Don’t know. I figure it’ll either wash off with detergent and water, or it’ll take a “strong” solvent like xylene or acetone.
Ed
Thanks Ed. The foam came off with a dry paintbrush. Those crystals are right around a solder joint, so maybe it is from the flux. I was just a little afraid to use anything stronger than alcohol at first. The engines are unpainted, so the darkened areas should be covered anyway.
Is the metal itself discolored? Or is there a clear lacquer coat over the whole thing? If it’s a clear coat that’s been discolored, it can simply be stripped off with something like lacquer thinner, and then a new coat can be added if you want to maintain the brass color.
I would think the value of the brass locomotive just dropped considerably after being stuffed away in a non-protected container for that length of time, you and many others are in for a big surprise when these dinosaurs actually see daylight covered in green kryptonite and large chunks of foam welded to the brass, good luck.
I don’t think so. Almost 70% of the brass that’s sold on Ebay has some sort of tarnish from old foam. It doesn’t hurt the value to me at all. In fact most real MRR’S don’t run unpainted brass models on there layout, it looks stupid. So with a painting in order after buying it I wouldn’t care of glue was stuck to the brass engine. It has to be cleaned anyhow, primed and painted. So anything like tarnish will be covered over.
Mike
Running unpainted brass looks stupid! Now thats just a bit harsh wouldn’t ya say…
I’ve run one or two of my brass (unpainted) and never recieved a dorogatory response from viewers and as the old saying goes…There’s a prototype for just about anything bub.
Didn’t mean it to come across like that [:D]. But most unpainted brass doesn’t see a lot of time on a home or club layouts
Mike
Thank you to everyone who offered constructive advice. Ed, I already thanked. Darth, I think you are right. It is the lacquer that is discolored, not really the brass. Mike, you echo’d my feeling that if it is going to be painted, it really doesn’t matter. CB&Q, LOL, Thanks for making me smile. And Tatans, the first two have already sold for more than you can afford. But thanks for your opinion.
Greg,
At least you don’t have to strip it. Just etch it, prime it, & paint it. If you need some ideas just send me an email. I have painted MANY MANY brass engines.
Mike
Yes, but is not the engine in this picture actually painted and lettered? 
Thanks Mike, but I am getting out of the “large railroad” hobby. I will just keep a few things that can be used on a traction railroad that I may build. The rest will be sold.
Nah, it’s just got the largest set of decals that MicroScale ever produced, LOL!
Tom [:D]
There is a company in Massachuesetts I believe called Reboxx. They make replacement boxes with non reactive foam inserts just for brass locomotives. They may be able to offer some suggestions on removing stuck on foam and staining.
Alco, I am amazed that anyone even does this! You get the Award for “Most Unexpected Help From a Model Railroader”