After shaking the bottle for quite some time over 2 days to achieve a good mix I was astounished that the resin looked good in the vat.
See for yourself how the prints, primed and non-prime and painted figures turned out. This has been my first paint job ever so please bear with me
I cut all supports with the flexible extension of the Dremel 4000 and a cutting disc. Sanding has been done with a smaller diamond tip in the flexible extension - in the case of Dustins figure I removed the support points from his face with the sandpaper accessory.
Very surprised that resin that old performed so well.
One hint I can offer is to use needle files vs sandpaper or Dremel.
You could easily get the remnants of the supports to be flush with your model using needle files. They, like anything else, are in the “you get what you pay for” category. A very good set of needle files is easily over $100 but you can get a decent set for far less. Check jewelry supply places on the Net. The various grades of “cut” (coarseness) can be confusing as different countries have use different designations for the degree of coarseness. https://www.kmstools.com/blog/hand-file-identification/ This is a decent primer on file lore.
The files will cut the support nubs only (if used properly) where sand paper conforms to the remaining bump and thus only smooths it vs removing it (as can be seen in your photos). I’m not criticizing but just trying to help with your next project to get the results you probably desire.
LOL like a fine wine. I still have a 500mL Flex bottle, from the original formulation (before it was black, and before Elastic was a thing). Still printed last I tried it, but the prints degrade pretty quickly with too much compression or friction (in fairness I think that was always the case with the Flex v1 prints).
What does your shaker look like? You might get a laugh out of this.
I started off by shaking the bottle for about 30 minutes. After that i tried a print on my F1 and one on my Peopoly Moai. Both failed: only parts of the bases were printed. As the bases get a much higher exposure i increased the exposure of all layers by 10x. That worked and i could get a few successful prints out of it. But only for small parts and with poor reliability. And 10x exposure also means 10x printing time, so this was not really practicable.
I always wondered how SLA resin actually ages/goes bad. My current understanding is that it is by decay of the photoinitiator. As DLP resin is much more reactive i assume it has to contain a higher concentration of photoinitiators. So i tried mixing the old Formlabs clear resin with a DLP resin (FunToDo Clear). 380 g old Formlabs clear with 30 g of FunToDo resulted in a resin that prints at the same exposure as fresh resin. The following parts were printed with that mixture, the blue color comes from remains of Peopoly Blue resin in the vats and bottle that i mixed the resin in.
At the moment i print a larger part (12 x 12 x 1 cm) and it looks like that it will come out good. In the meantime have printed approx. 500 ml of that bottle, the blue tint is almost gone now.
Because the DLP resin is very reactive this method could possibly wear out the PDMS layer faster, but i didn’t print enough to say if this is the case or not.
The print quality is ok for my needs, i printed gears with 0.48 module and they work fine. So if you have time and motivation for experimentation this seems to be a practicable way to revive old resin.
