Opening a 'dead' spray can.

[G4XWDJim]

I've had three cans of black wrinkle finish in stock for over ten years. When they were new and in regular supply the spray output was very irregular and often blocked up. Sure enough yesterday when I tried to do a small job with one it blocked up and even with the nozzle removed pressing the little tube that sticks out of the top would not allow the paint to come through.

Clearly there is paint in there, it's almost new and unused and heavy so I thought I'd take it into the garden and punch a small hole in the top to allow the air pressure to release prior to cutting off the top with tin snips.

I realise this might be a dangerous activity but if I let the can settle for a while and punch a hole with a scriber, on the top side away from me, into what must be an air space I should render the can safe and can then re-use this rare paint in another manual spray gun.

Does anyone have any thoughts on this procedure or better still has anyone done it before.

Jim

[Phil G4SPZ]

Hi Jim. I'd clamp the can firmly then drive a small nail in near the top. The nail should remain in place leaving the propellant to leak out slowly. I think it might not be air - old aerosols were commonly pressurised with CFCs ('Freon safety propellants') which are of course banned from atmospheric release by international law!

[mark pirate]

I have a fair few spray cans that are over 20 years old, some of which are still fine and spray properly.
I always shake them for at least 5 minutes before trying, but I have some that appear to have lost all pressure, but the paint is still fine.
I drive in a panel pin at the top of the can through a rag to stop the paint going everywhere!
Always do this outside, as it can be messy. I then transfer the paint into airtight jars for future use.

Mark

[paulsherwin]

The propellant might well be propane or another inflammable gas, so you should bear this in mind.

I would drill a hole using a Dremel and very small bit. The can should start to vent slowly as the bit starts to penetrate, and the process should be more controllable than using a nail.

[kalee20]

I'd put in in the freezer first for a few hours, which will reduce the pressure. Then do the nailing / drilling inside a plastic bag.

Have fun!

[G4XWDJim]

Thanks for the ideas folks.

I liked Paul's idea of using a small drill but was worried that I might end up filling the chuck with paint so I used Marks idea of a panel pin through a rag. A quick tap and a hole sealed by a panel pin allowed the propellant to gently vent itself. Not known for my patience which was wearing thin after two minutes gentle hissing I pulled out the panel pin. Whoops!

Fortunately the rag was controlling the outflow which didn't last long and the black patch on my lawn is rather attractive and a distinctive new feature..

After I'd cut the top off I noticed a distinct bubbling coming up through the paint which continues some 20 minutes after I'd transferred the paint to a jam jar. I'm reluctant to put the lid on.

I wondered whether because this is wrinkle finish paint there is some sort of additive in the paint that causes the wrinkle reaction. Will I ever be able to put the lid on. Talk about Genies out of bottles.

Jim

EDIT.
I've just checked the temperature of the jam jar 30 minutes later to find it's very cold which to me suggests that there is still some propellant escaping but where is it coming from, does it combine with liquid paint.

[kalee20]

My comment posted just too late then

The bubbling will probably be evaporating propellant. If you feel the jar you will find it's cold - the initial evaporation causes cooling, and the vapourisation of the remaining propellant is thereby slowed down. But it still continues till it's all gone.

I have with varying success re-pressurized cans using a butane lighter filler (get one with all the adaptors in the lid), as said before pop the can in the freezer for a bit first and warm the lighter gas can.

[G4XWDJim]

The problem I've always had with these wrinkle finish cans, even when they were current production, whether made by Sperex, which this one was or Hycote which I've commonly used is that they always seem to clog up internally and not just the outlet nozzle. I submerge them in very hot water which seems to help but I think it was uncommon to get one that worked properly until it emptied. I always used to try them in the shop before paying for them as it was not unknown for them to block whilst still on the shelf.

Jim

[Junk Box Nick]

I used to use a lot of spray glue and kept a stock of spare knozzles as they were always blocking up. Blocked ones I would recycle by soaking them in solvent.

The other day I used some WD-40 on a hinge. I always have several cans but this had been languishing at the back of a cupboard. I noticed a holiday competition sticker on the can. Closing date can just be made out as 31 March 1992...

[ben]

For spray paint, after use you should always hold the can upside down and press the nozzle until only air comes out. This should stop paint drying on and clogging the tube and nozzle.