cleaning hard rubber tank

I recently purchased 4 8x10 kodak hard rubber tanks.One tank was used as a fixer tank for B&W film processing and you can see the silver has coated the tank sides.Any suggestions as to how to clean this silver off the tank sides?.

Thanks,

Doug

Doug,
I am inclined to think that particular tank was used for developer. I would get silver deposited on parts in my film processors; but only in the developer sections. Fix sections were typically very clean. Kodak used to supply a developer system cleaner which IIRC was Sodium Dichromate and Sulphuric or Nitric acid. Safe enough if used properly. I do not think you really need to remove it, as it should not interfere with future developing.

Doug;

It might be a sulfur deposit from the hypo going bad. If it is silver, a mixture of dichromate and sulfuric acid will remove the deposit, but if it is sulfur, only elbow grease and a good abrasive pad will do.

PE