I think it's important to share our biggest most shameful mistakes too in the spirit of learning, here comes one of mine

Should've googled "ammonia + acrylic" and skimmed to the middle of the page beforehand

This is what it does to a crystal (used a "magic" watch cleaning solution that is mainly weak ammonia, better than my stronger ammonia, have awesome results with most things):


Could've not cleaned this crystal as well, but it had some adhesive on the sides, should've used soap water and clean with hand, luckily I hoarded many spare crystals so it doesn't ruin my day

 

Also if anyone needs a lightly used acrylic crystal that could use a slight polish, I'm your guy

 

Yeah, I learned these lessons years ago with servicing hi-fi equipment, some seemingly benign chemicals don’t respond well to certain material. For cleaning I kept iso alcohol, denatured alcohol, Naptha, Deoxit, and rubber restore at my bench. Every one of them have a particular application and can harm materials that may seem robust. I found Naptha (lighter fluid) to be one of the best chemicals to remove adhesives and nasty funky without harming 99% of materials- also fast drying so good for things that can’t get wet.

 

Thank you for the Naptha suggestion, just ordered some, I find it hard to find local versions of English chemicals, for Naptha I got a colourless lighter fluid that's marketed as chemical grade and aimed for cleaning too - so I guess it's a match - just searching "Nafta" doesn't yield any results online, though I've heard it being used in watchmaking locally - so at one point old and online disconnected and the product name didn't continue

 

My spelling was incorrect, apologies - it's “Naphtha”. But it seems that you found it as a colorless lighter fluid. It’s listed as a hazmat due to its flammability. Don’t leave your lab stove on when you pour out this stuff.

 

Same difference on my side, sadly no one uses the name any more

 

Try "Colman Stove Fuel". They sell it by the gallon. White Gas is another name. So is Benzene.

 

Got a lighter fuel after @JwRosenthal 's suggestion, but like I said the content and naming changes a lot from country to country, Benzene here means gas you put in cars, which is also used for the purpose of cleaning, but the purity/additives are worrying

Since this one is aimed at cleaning and colourless, I hope it's in a pure form

 

Art conservators use Naphtha quite a bit for cleaning of fine art. It takes grime and surface contaminants off without damaging paint or other materials underneath. Obviously having an understand of what materials are being affected and applying to test areas are part of the process.

 

By the way lighter fluid as it turns out can ruin acrylic crystals too

But I believe it just exposes surface cracks, and not actually cause them, so this could be a good thing or a bad thing, I think it's bad

Had a crystal in bad condition, I assumed it was cracked, there was definitely a bump, after sanding and polishing it turned out spotless, I was pretty excited and honestly I didn't need to clean with benzene as there wasn't any polishing compound gunk on the crystal

I hand wiped it using the lighter fluid and after the cleaning process all the surface cracks were exposed

To test and prove this theory somewhat, I polished the crystal again and it filled the surface cracks!

Before cleaning, it turned out perfect after sanding and polishing:


After lighter fluid cleaning, before re-polishing:


Quick re-polish using compounds to see the result:


So maybe the ultimate result here is that polishing compounds can fill surface cracks

Recently on a watch I wondered why the polisher left gunk under the crystal and not cleaned it with benzene etc. - this is likely the reason

I bought Turpentine to see whether it's less affecting

 

It's the same thing. We call it white gas here in the States because it's gasoline without any additives.

I keep a few cans in the garage in the event that society collapses.