Ever since we developed Multi-Etch in 1993, we have always used it heated because it is much quicker than using it at room temperature. Recently we conducted extensive experiments to compare the efficacy of heated vs room temperature. What we discovered is that over time, whether heated or unheated, unused Multi-Etch solution etches faster than when it is first mixed up. But the difference takes months to notice.
We also discovered that if you heat the whole solution just one time to 150 degrees Fahrenheit, i.e., bring it to a boil and turn it off, that activates the solution and it will work much better at room temperature from then on. If you don’t have equipment to heat up Multi-Etch safely indoors, take a hot plate and a simple double boiler outside and heat it up there. Once it’s boiling or close to boiling, you’re finished! You can then use it while it’s still warm or let it cool down and use it unheated. But, it will always work faster if you can use it heated.
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