Quick VAT rehab
I have found my calling as a VAT killer. FEP can't take more than one or two attempts before I get it to fail, so I print bareback.
Consequently, I destroy a lot of PDMS layers, and usually in such a way that I have an acrylic on acrylic mess after the damaged pdms is removed. If you get away without having cured resin stuck to the bottom acrylic, the PDMS layer can be rehabbed in as little as 4 hours, start to finish.
I tried QSIL at room temperature first, but the edges never cured, even after 5 days. Being impatient, I turned to the following process.
QSIL 216 (around $35 on amazon - the 1pt kit will rehab 5 to 6 vats, or in my case the same vat 5 to 6 times)
A sharp knife
An accurate gram scale.
Mixing cups and stirrers.
Convenient tools to remove the existing silicone.
Your kitchen oven.
Use the knife to slit the silicone along the edge of the vat. Once you get one edge free, you can usually pull the whole layer out in one piece.
Use your fingers to get anything still on the bottom off.
You will probably need a tool to get the stuff around the edges and corners - I use a flat head screw driver.
Wash the VAT in soapy warm water. Dry completely, and inspect for remaining silicone and/or surface scratches (if you have scratched, no worries, it's just going to take a bit longer)
If the vat is clean and dry, you are good to go.
get out your QSIL, mixing cups, and tongue depressor stick stirrer. Measure out 6 grams of part B and 60 grams of part A. Mix for about 3 minutes, making sure to scrape the sides and bottom of the cup.
You are going to make lots and lots of bubbles. Don't fret.
Once mixed, use a "high pour" to drizzle the silicone into one corner of the VAT, allowing it to flow into the rest of the surface.
Once you have poured it all, you can assist the coverage by a few tilts, making sure the mixture has reached all edges and corners.
Then place the vat on a level surface and let it sit for an hour or two. Most of the bubbles will have disappeared.
Use compressed air, to gently disperse any bubbles that remain, or to drive them to the edges or corners where they won't matter.
Turn your oven on to it's lowest WARM setting. You are shooting for roughly 100 degrees F, give or take. My oven dial has the word WARM on it, I set the pointer to the R in WARM, with is well below it's first listed temperature of 200 degrees.
pop your VAT in to bake. Check it in a half hour. If the oven is too hot, the walls will be bendable - turn down the heat a notch. If all looks good, let it cook for another hour and a half, then check again.
It's done when a puff of compressed air no longer will move the surface in the corners and edges (don't test the middle! it cures first, and you don't want do disturb the nice smooth surface).
If the corners and edges are set, you can remove the vat and use it right away.
If you were unfortunate enough to have cured resin stuck to the bottom of the vat, under the PDMS - there's a lot of pia work to do.
1st, you have to shave / scrape the cooked resin off while drying not to scratch the surrounding clear acrylic too badly.
When you get down to the last bits, sand the remaining off using automotive wet/dry sand papers. I usually redo the whole bottom of the VAT just for good measure. If the scratches are very shallow you can try starting with a 400 grit paper. I botch things up much worse, so I start with a 180 or 220 grit, then follow with 320, 400, 600, 1000, and 1500 (I told you this was going to be a bit more work).
If you happen to have 3M polishing papers, you can use them too - 4000/6000/8000 grits/mesh.
Finally, apply some metal polish (brasso) and buff it off.
wash and dry
Now you're ready to mix, pour, and cook as above.