Tin Pest in Toy Soldiers

You cannot prevent tin pest. It is caused by a crystal transformation that takes place at 13.2 C, when it goes from tetragonal to cubic structures; the lower the temperature the faster it goes into cubic. However, this temperature is only relevant for pure tin. I have never seen tin transform at this high temperature and it normally needs significantly sub-zero temperatures to make it turn. To avoid getting tinpest, I would recommend you use impure tin - this reduces the transformation temperature even more and helps prevent the formation of the (bad) cubic structure. Alternatively, make sure you keep your tin soldiers at above 13.2 C.
I believe that Napoleon Bonaparte had one of his generals executed because he shipped tin from Russia and on receipt in France it was a grey mass, not the bright shiny stuff he expected. Anyway, Napoleon thought the general had robbed him, so he dispatched him to the next world....

If you are really sure that it is tin pest you must remove all powdery tin and then immerse objects in melted parafin wax (115-120 °C, 4-6 hours!). Keep cleaned objects at room temperature 18-20 C(never below 13,2 C!). ope it helps and good luck!

According to Russian book Himiya v Restavracii,Leningrad 1990.