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I googled Coleman fuel and read that it is a mix of several flammables and not straight naphtha so I am reluctant to use it, not knowing how it affect stamps.
The Material Safety Data Sheet stated about two years ago that it was 100% naphtha. If there are any other substances they would only be there in trace amounts, Google not withstanding. (Naphtha itself is sort of a generic term, and may be any of several substances.) I don't know if Coleman's formula has changed in the past couple of years. I've been using Ronsonol/Coleman fuel for years with no ill effects on me or on the stamps. The can that I have right now is not Coleman brand, so I can only assume that it is identical. I don't know what you might find in it in Guatamala, so try it on inexpensive stamps first.
Quote:Ronsonol no longer contains naphtha. The following link is a Martin Guitar site but it has information that will be useful to anyone who believes Ronsonol is basically naphtha.
http://theunofficialmartinguitarfor....UoTtp5R4ZXc HAHA I was a moderator on the UMGF site for several years...funny you picking that one. Incidentally, the UMGF is an independent non-profit organization, not owned or controlled by the CF Martin company.
As far as Ronsonol not containing naphtha any longer: the MSDS states right on it that it contains 30% naphtha. I haven't tried the new formula so I can't say if it works for watermarking or not, but I would bet it will. Again, try it first with inexpensive stamps.