The new vat will include a "Dam" that will allow us to pour a flat coating of PDMS without any slope and provide for a clean "cliff" separation. The waterfall method works, but applies some downward forces that try to suck the new layer over the waterfall and that can lead to part failure, most notably it increases the likelihood of ulcers in thin vertical walls.
The problem with simply using a flat vertical (removable) dam has always been the meniscus. As you can see in the image below, the dam design includes a "meniscus trap" that makes it easy to trim it off after the pdms has cured (and before the dam is removed).
Steps to recoat:
1. Clean the vat and carefully remove the old coating.
2. Place the Dam about 5 mm from the edge of the glass (see the image above).
3. Mix up ~50 grams of Sylgard 184 (PDMS)
4. Set the vat on a level surface and pour the PDMS over the glass. The air bubbles in the PDMS will pop before it cures, do not be concerned about them.
5. It takes about 48 hours for the PDMS to cure at room temp. Or you can use a hot box at about 160 degrees F for a couple of hours.
6. After the cure is finished, carefully cut the pdms along the dam (see image above) and remove the dam along with the meniscus portion of the pdms.
The vat is ready to go again.
Measure Twice, Cut Once.