These are a few observations on PDMS clouding. I use 1:1 mix (primarily because it shortens build times due to very short exposure times) and on the present vat on my 1.2 HD machine I have 70 hrs of lamp time (started at 35 hrs and is now at 105 hrs). I do leave the resin in the vat between prints unless it needs filtering. I have stoped cleaning the vat with alcohol or water, I only use paper towels. I had noticed that when u put the model in the ultrasonic that the uncured resing came off as a white milky substance, could this be what exasurbates the clouding of the PDMS (reaction of water with the resin that has seeped into the surface of the PDMS). Since I have discontinued water or alcohol in the vat the number of hrs on the PDMS has def increased. I even posted a picture at 50 or 60 hrs and there was no clouding of any kind. I will post it here again. I am just starting to get some clouding and it started at about 65 hrs. The strange thing is that they are not support based clouding (small circles) but a light clouding of the entire print area (30 xy area). Can't really see where prints were done. This is the first time that i have cleaned and strained resin over an extended period and never let alcohol or water touch the PDMS. There must be some correlation here. I wish some others would try cleaning with paper towels only (I do drain the vat well and use a silicone scraper to squeege the surface) and see if they experience the same non clouding PDMS.
I don't know if u can tell from the pic, but there is no clouding at over 50 hrs of printing. I always print at or near the center. I did not move prints around on the PDMS purpously just to see how long it would take to start clouding. All of the 50+ hrs was at 30 xy 30 z and using 1:1 mix. I also think a contributing factor is the short exposure times with this mix. I do 2 attach layers at 6 base and 1 over and subsequent layers at 1.500 and .50 seconds. I always use 1mm subsequent overlift and 4 sec settle time.
I am convinced that this extended PDMS life is due to short exposure times (mostly 1.5 seconds and less) and the absence of water and/or alcohol coming into contact with embeded resin in the surface of the PDMS.
The resin u see along the edge of the PDMS (i still cover entire vat, don't use saver method with the dam) is resin that has gotten down between the PDMS and the sufrace (side walls) of the vat. Can't wipe away with paper towels, but it doesn't matter. Resin left in the vat when cleaning is not an issue, particles in the vat are a problem.