Resin replaces filament as the material you handle most on the Mono 4, and it needs different habits. Gloves and safety glasses go on before the bottle cap comes off, every time, not just for the first fill.
Shake or stir the resin bottle before pouring. Pigments and additives settle over time, and an unmixed bottle can print with uneven color or inconsistent curing. Pour slowly into the vat up to the marked maximum line, never higher. Overfilling risks resin spilling near the build plate mechanism or the screen area as the plate lowers into the vat.
To change resin type or color, drain the vat rather than pouring a different resin on top of what remains. Tilt the vat carefully and pour the leftover liquid through a fine filter back into its original bottle, catching any partially cured debris. Wipe the vat and FEP film clean with a lint-free cloth and a little IPA, and check the film for scratches or clouding before adding the new resin. Mixing two different resins in the same vat can affect cure behavior in ways that are hard to diagnose later, so keep them separate.
Between sessions, close the printer lid to block ambient light and cut down on odor in the room. Cap resin bottles tightly right after pouring and store them away from direct sunlight and heat, ideally in the same cool, dark spot every time.
Leftover resin from a canceled print or a vat you are retiring should never go down a drain. Spread it thinly in a disposable container and let it cure fully under sunlight or a UV lamp, then dispose of the solid, cured resin as solid waste, following local rules for chemical or resin waste.
These habits build on the safety routine covered in the printer setup guide, worth a look if you have not been through it yet. For the vat and screen care that goes alongside resin handling, the maintenance schedule covers FEP and LCD checks on the same rhythm as fill and change days.