Decanting paints

Decanting paints is a process of getting the paint out of the spray can and into a bottle / jar. Why would you want to decant your paints? Main reason for doing so is to use it with an airbrush. It allows for a better control than a spray can. More control is less wasted paint and more bang for your buck. Why would you decant instead of just buying paint bottles? Well, maybe you want some unique shade that only comes in spray cans. Perhaps spray cans are the only paints you have easy access to. Or maybe you switched from spray painting to airbrushing and still have a bunch of half-empty cans cluttering your workshop.

Whatever the reason, let’s skip the why and learn the how.

Materials needed

Preferably we want to do it outside or someplace well ventilated. This process takes quite a while and there will be paint vapor in the air throughout. Make sure you use your respirator.

First off, here’s what we’ll need:

1. Some spray cans (in my case some Mr.Topcoat Gloss leftovers)
2. Paint bottles (or some other sealed container)
3. Plastic straws
4. Some tape (basic masking tape works well)
5. Some tinfoil

Decanting process

Using the tinfoil we create collars around the bottles. It will help prevent paint escaping the bottle as we spray it. It will also stop dust from getting inside the bottle while still allowing propellant gas to escape.
Next, we give the spray can a good shake and put a straw over the nozzle. Secure it in place using a good bit of masking tape.
Finally, we can start spraying paint into the bottle. Important – avoid filling the bottle above 75-85% and whatever you do, don’t let the straw sink into the liquid paint. It’ll most likely end with it shooting out of the spray can, spilling paint everywhere.
You’ll quickly notice the stuff that comes out looks like a bubble bath. We want to spray in short bursts and wait a bit for it to settle into liquid to avoid having it run out of the bottle. BONUS Physics lesson: You’ll also notice the stuff is really damn cold. As the gas passes from high pressure to low pressure environment, its volume must increase and/or its temperature must decrease to compensate. Yay, science!
Once we’re done, we want to leave the bottles uncapped for a few hours to allow propellant gas to escape properly. As I mentioned earlier, we leave the collars on to avoid any dust getting into the paint. Don’t worry about paint curing/drying, it’ll be just fine.
There we go, all bottled up. Waiting time might differ depending on the brand and temperature you’re working in. Try to carefully stir the paint with a skewer – if it starts buzzing stop immediately and give it some more time. If it doesn’t react, you’re good. This batch of Mr.Topcoat was ready in about ~3 hours.

This is it. Decanting paints is not as scary as it might seem. Just make sure to not rush it and allow plenty of time for propellant gas to fully dissipate before sealing the bottles. Most brands should be ready to airbrush once decanted, but use your judgement. If need be, dilute them using appropriate thinner.