Rules for using resin printers

The first rule for setting up a resin printer is hazard planning. Do buy a pack of cheap nitrile gloves as everyone says, and create a workspace that is clear, organised, and uncluttered.

Hazard planning

Assume that you WILL at some point end up dripping resin somewhere.

Create a protected “splash zone” around the printer, around your cleaning station, and (if they’re not adjacent) along the path linking them. Make sure that you are not working above a piece of treasured furniture, or carpet. If the printer is a small one, considered getting or making a tray to sit the printer in, in case of spills. An upturned cardboard box lid works, as does those cheap foil disposable oven trays used to roast turkeys at Christmas.

Have a spill strategy: a roll of kitchen paper towel and a bin (for disposability, perhaps even another disposable cardboard box, with a lining). Have disposable tools handy: packs of wooden spatulas or bamboo skewers are good.

Since the resin "goo" does not evaporate, or harden without UV light, once it is on a surface it tends to get spread around by contact contamination, surface to hands to surface to hands. Remember that even when you’ve wiped down, there may be a smear of liquid resin behind. If you have a UV lamp or torch handy (which you probably do if you’re working with this stuff), you can use that to cure the residual smear to harmlessness. Some people might consider spreading the working surface with newspaper before each print session and throwing it away afterwards, after exposing it.

Wear gloves. Yes, I know you think that you’re too careful to need gloves, but once you’ve wiped away that drop of resin, when you touch the surface to check that it’s clean … and find it isn’t … you have it on your fingers. Even with that blob of stray resin that you zapped to harden it, it’s tempting to pick at it to check that it’s hard all the way through, and when you find it isn't … you again have nasty greasy resin on your bare fingers.

If you have a bright UV lightsource for curing, “zapping” your used wipeup tissues to turn the toxic goo into inert plastic is a useful idea (because otherwise you =were= going to take them to a special toxic waste disposal site, weren’t you...). Consider regularly "zapping" your entire work surface and tools.

Resist the temptation to remove the stuff from your skin by curing it. Curing it makes some resins get hot. This provides the opportunity to both give yourself deep burns and possibly trigger an immune reaction to sensitise yourself faster. If you are going to be waving strong UV lamps about, post-spill, wear UV-protective glasses (usually yellowy-tinted). UltraViolet does nasty things to eyes. You ==do have== some of those, don’t you?

If you’re not using a dedicated curing station with a UV filter, again, UV goggles for eye protection. And of course, remember to put away all your unexposed resin before waving UV about.

Print cleanup

You’ll probably have a solvent tray for washing the excess goo off the printed pieces before final curing. Decide on a disposal strategy beforehand. Even if it’s a water-washable resin, remember that there’s a certain amount of the material going to end up in your washing fluid, and even if the fluid is water, technically, the mixture shouldn’t go down the sink.

Some people have talked about letting the washing fluid simply evaporate away, leaving the goo behind (which can then be zapped “hard” with UV light or direct sunlight). But with alcohol-based solutions, bear in mind that saturating your house or room with highly-inflammable alcohol vapour is not a great idea. Evaporation is perhaps a less bad idea if you have a big garden and it’s summertime (in which case the tray can be turned to point to the Sun, and the residue can then be left to bake hard in the UV-rich summer sunlight).

If you’re taking the alcohol cleaning route (which most people do), methylated spirit is essentially almost pure ethyl alcohol, deliberately contaminated with enough methyl alcohol to make it poisonous, plus a purple dye. The purple dye is not likely to have any perceptible effect on your prints, and for those with super-eyesight, given that yellowing can be an issue with over-curing, perhaps a ==tiny== bit of residual purple might not be a bad thing. But bear in mind that you are then dealing with aa substance that is deliberately poisonous, and also breathing in the fumes. “Denatured” alcohol is essentially another name for ethanol that has been deliberated "tampered with" by the adding of something poisonous (usually methyl alcohol) to make it unfit for consumption. Methyl alcohol is nasty stuff that can turn you blind or mad, or both. This allows it to be sold without incurring the extra taxes that apply to “drinkable” alcohol.

Meth bottles, for some reasons, tend to be tall and made of squishy plastic, and if they’re not stored in a bay, they have a tendency to get knocked over.

Some people may invest in one or more plastic buckets with hinged handles as a way of transporting bottled “spillables” like resin and alcohol. A bucket is more difficult to drop than a bottle, it’ll be carried lower to the ground, the bucket rim makes it more difficult to knock a bottle over, and if it does happen … the spill goes into the bottom of the bucket.

A bucket (round or square) can be useful for storage. Consider having one bucket for bottles and another for clearup materials. And maybe a spare, to use as a bin. Once you’ve washed your print in a shallow bath, how are you going to carry a shallow tray of contaminated solvent across the room, safely? In the bottom of a bucket. If you don't need all the buckets, they can usually be stacked

Some would suggest alcohol wipes, which are cheap, but fiddly to open quickly in an emergency. These usually use isopropyl alcohol. If you already have the alcohol and the wipes to hand (and you’re not going to fumble with the alcohol bottle and spill it), then perhaps having dedicated wipes as well might be unnecessary ... although in a COVID world, you can always carry a few around with you in a coat pocket.

Once you’ve finished a print, it’s suggested that you clean and empty the print tank, and filter the resin to remove any “bits” – if a rogue piece of cured resin is in the tank, and you start a new print, and the build-plate clamps down onto the print film and traps the lump, then you can damage the film. This of course creates an excellent opportunity for creating spills and creating messes as you pour stuff in and out of containers. If you’re not going to be using a new filter every time, then you will also need somewhere to store a goo-contaminated filter (which is likely to remain a bit goo-ey even if washed) until the next print. Preferably something with a lid.

Consider filtering into a spare tray, as a filter loaded with heavy resin on top of a tall bottle tends to be a topple hazard.

If you’re filtering the resin, you also need some sort of extra tray or container to receive the resin before you put it back into the print tank (or a bottle). Some people might prefer not to pour the used resin back into the bottle, and to keep a distinction between fresh and semi-used resin (in case part-cured resin starts a chain reaction). Since you’re not supposed to leave resin in the print tank for too long this means that you’ll want extra light-safe containers between print sessions.

You’ll also probably want extra storage bottles or containers if you are messing around with pigments, to hold the unused colour-modified resins.

Since nitrile gloves are so fiddly (and messy) to put on and take off, a longer-term solution may be to invest in a pair of larger slightly-oversized heavy-duty "industrial" rubber gloves that can be slipped on and off again easily without transferring what's on the gloves onto your hands.

At this point you'll realise that working with 3D resin is a bit like working with nuclear materials: every step that you use for safety seems to end up generating more things that need washing, and more contaminated waste.

Star tip: Barrier cream

Since it's so difficult to completely avoid getting resin on your hands (because of secondary contamination, the fiddliness of putting gloves on and off, and the chance of accidentally cutting a glove when you're trimming a piece), consider investing in a tube of barrier cream and applying it every time you're going to be handling your printer, tools, or resin -- it's a good second level of protection in addition to the gloves. Bear in mind, though, that while barrier cream might stop pure resin getting into your pores, it's going to be much less effective with respect to "washing alcohol", or alcohol with resin in, as the alcohol will tend to dissolve the fats and oils in the cream.

Hardware store shopping list:

• UV light (~405 nm wavelength)
• Nitrile gloves
• Cleaning fluid – a decent quantity of isopropyl alcohol, ethanol or methylated/denatured alcohol.
• Buckets with handles (and lids, if you’re also using them for storage)
• Paper “kitchen roll”
• Washing bath / trays for filtering resin
• Container for used washing fluid (if the “bath” doesn’t have it’s own lid)
• "Tupperware" or other plastic boxes with lids?
• Craft knife/scalpel
• Bin

Poundland!

Poundland sell small packs of nitrile gloves, kitchen roll, and small plastic containers with lockign lids. Look out for the three-packs of clear 200ml containers, with colour-coded rubber seals, three for a pound. These are the ideal size for decanting unused resin from a small resin printer’s vat. I used the grey-coded ones for resin, the yellow ones for solvent, and the blue ones for holding small parts. Since these little containers are clear, they are probably not UV-safe … but Poundland also sell mod-sized cheap-and-nasty black plastic stackable storage boxes for a pound each. So you can use the little containers to keep your stocks of unused resin in different colours, different mixtures, and different custom colours (if using a CMYK colouring kit), and see what’s what, while keeping them all UV-safe together in the larger black container.