I recently bought a watch cleaning machine from a retired watchmaker, when I collected the machine the jars already contained solution, the watchmaker told me the rinse jars contained isopropanol. I did ask him what effect on the shellac holding the pallet jewels would the isopropanol have, saying I would be worried that it would dissolve. He said he had used it since Benzine had been unavailable to use, and as long as I rinsed for no more than 15min in each wash there would not be a problem. He also said it was very quick to evaporate in the drying stage and left no residue.
I have ordered new cleaning solution and rinse solution from Quadralene and intend to use these.
I have though cleaned 4 watches last week in the solutions in the machine and have not had a problem.
Today I decided to test and see how long it took to actually dissolve the shellac,
The image above shows 3 Russian and one Swiss set of pallets and the shellac can clearly be seen. I have been using the solution for 15min each rinse and have not had a problem so I put the pallets in a isopropanol rinse for 1hr to see what effect it had
On the Russian pallets it has greatly degraded the shellac and almost totally washed it away on one, but on the Swiss pallets it has not even touched the shellac on those.
I will not use isopropanol again in a cleaning machine and intend to try a similar test with the Quadralene rinse to see how shellac friendly that is because the data sheet doesn't specify what ingredients are in it, but quadralene did tell me they have many watchmakers who buy their rinse and have not had any problems.