405 nm wavelength should be sufficient for curing resin parts. Cure times can depend on the type of resin you are using:
Castable - 2 hours
Tough - 45min
Everything else - 45min to 1hr
The water method is interesting, as it’s a good way to have the UV light diffuse around the piece. If you have something like the solar powered turn table recommended…this essentially achieves a similar effect. I haven’t tried the water method myself, but people seem to be getting good results.
IPA saturated with resin will lose it’s cleaning effectiveness over time. Honestly, I’ve never really looked into filtering the IPA…but now that you’ve mentioned it, I’m going to speak with some of our material techs today. If I find an easy filtering method, I’ll definitely do a post about it.