"Etched brass - Deteriorating over time?" Topic
8 Posts
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Virtualscratchbuilder | 27 Jul 2014 12:24 p.m. PST |
Question: I started working on a Langton 1/300 Juno that has sat incomplete in my closed for about nine years. I started working on the etched brass sails, which are usually a snap, and I am having all sorts of problems. Even after washing, rinsing and drying, they will not take the usual glue nor are they behaving when I get so far as to paint them. In some places the paint has curdled and lifted right off the surface, primer and all. It is not a mater of lingering detergent or other agents such as grease or finger oil. Does brass deteriorate and change chemical consistency over time? |
bc1745 | 27 Jul 2014 12:45 p.m. PST |
Brass does not deteriorate over time ….it can be affected by sea water and may leach zinc if used in aquatic applications but it is a very stable in all other applications |
BrianW | 27 Jul 2014 12:46 p.m. PST |
That's very interesting. Have they been stored in a plastic bag? If so, maybe there has been some chemical reaction between them? (This is just a WAG on my part.) BWW |
BrianW | 27 Jul 2014 12:47 p.m. PST |
Hmmm, bc1745 answered my question. Perhaps it's a problem from the other end; i.e. how old is the primer? BWW |
MetalMutt | 27 Jul 2014 1:27 p.m. PST |
the etching process necessitates the application of a "resist" to the brass (or nickel silver, steel, whatever) which prevents the acid etchant from eating away a particular area of the metal sheet. It sounds to me as though there is some chemical reaction occurring between your paint and either the resist or some age produced residue of the resist. Either way my recommendation would be to rub the sails down with some sort of abrasive. If still flat I would use wet and dry sheet (used wet) if they have been shaped (as I suspect your sails have been) then a fibreglass brush (aka a "scratch pencil") will do the job. Once you have brightened the surface of the metal then clean in the usual way before priming. |
Virtualscratchbuilder | 27 Jul 2014 1:47 p.m. PST |
The problem was before primer and before paint – after washing, rinsing and drying they would not take the glue, shaped or otherwise. MetalMutt, you are probably close as in many places the brass was very dull and splotchy on the non-etched side, which would have been 100% in contact with the resist, if I understand the etching process correctly. 300+ kits with etched brass, this is the first time it has acted this way, and the only uncommon denominator is the near-decade the sails sat in their original packaging. Thanks for the comments everyone. |
Fizzypickles | 27 Jul 2014 5:04 p.m. PST |
Acetone or rubbing alcohol should cleanse the surface of anything I would have thought. I always understood that self etching primers were the bomb for special metals like Brass? |
screw u | 29 Jul 2014 12:23 p.m. PST |
Wash them with alcohol as well as water, that way you are covered whether there is a polar or non-polar residue. Something might have leeched out of a plastic bag or container. Discoloration other than simple dulling can mean either oxidation, which is normal, or a chemical reaction with some substance which of course is not. You might also try a light application and buffing with a substance like "Brasso" which we used to use on our uniform brass. Admittedly I have never tried it on photoetch. |
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