It looks like you just debunked a phenomena we took as a fact of life.
Could the boiling action of the metastannic acid in HCl be the oxidizing factor, like incinerating, so that HCl can attack it? Like oxygen and HCl can dissolve copper, but HCl alone can not.
Good find, so you suggest to use this procedure to be able to filter pm dust and foils from the soluble stannic acid and recover the tin before converting with aluminum to stannous chloride.
For those cases where the tin paste can not easily be avoided, it will be a great option.
