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Degradation of lead and Britannia fittings


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Appears I may be stuck with lead fittings with Mamoli CSS Aabama. Can they be properly treated other than primer or watered down white glue to slow down the degradation of the lead over the long run. Does this problem also plague Brittania metal fittings.

Would wood or brass copies when feasible be better. Could not find Metal for dummies #2 at Amazon.

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John,

 

I would think that a clear coat of the organic solvent sort would buy you time, but if the "white glue" is PVA, that has the potential to be a disaster.  The final product in lead disease is lead acetate -I believe.

I am not sure how much if any acetate is in bookbinders PVA,  but all other woodworkers PVA has as much acetic acid as 5% vinegar.  My guess is that a PVA coat would accelerate the disintegration of a lead casting.  

The clear coat using lacquer et al. has the disadvantage of not being glass and thus allowing gases to migrate across it.  A quick smell of vinegar tells you that acetic acid is partially a gas at RT.  

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  Lead (or more likely tin/lead) fittings will be soft and bendable.  If primed on all surfaces (not sure which primer works best for tin/lead - but what is sold for cast military figures and 'flats' is obviously suitable), then painted with enamel (not acrylic) - they can last a long time without oxidation, since oxygen won't go through the coatings.  I found a painted CW tin/lead soldier I cast as a boy over 50 years ago, and it is in perfect condition.  Antique figures can be so found, as long as the coatings don't get scratched or chipped.

 

  Any lead in these figures has been banned for some time, so tin based 'pewters' have been used.  95/5 tin/antimony is "out" these days because of the antimony.  Something like 2% copper is alloyed with tin ( to make Britannia metal), since pure tin degrades under freezing temperatures.  (Napoleon's soldiers buttons fell apart on the road back from Moscow.)  One can see 'Britannia metal' (tin-copper) plate wear over 200 years old on display in museums in excellent condition, whereas the cheaper stuff with lead go dark grey and can oxidize in high humidity.  Conclusion ... Britannia metal is fine without painting for centuries - now I'm not talking about buried in soil, which will ruin anything other than gold (or platinum).

 

  Some kits have zinc metal castings, since anything with lead these days is a no-no.  Zinc can likely take the same primer, although zinc chromate is the best.  Some early zinc cast toy locomotives had zinc with contaminants and suffered from an internal degradation that caused them to crumble from the inside in spite of coatings.  I'm talking about stuff from the 1920s and 30s.  Since then, there are no reports of 'bad' zinc.   Johnny

 

  

 

 

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