does paint go off?

[scubabob]

i recvently opened a tin of ceiling white, well known reputable brand, that had been sitting in my shed for about a year or so and it had all seperated of course, but stink! smelt pretty bad, so i turfed it, wasnt game to put in in my house.

Does it go off or was it just some part of the paint compund i was smelling that one doesnt normally smell when its mixed up?

[journeyman Mick]

Your nose knows Yes, acrylic paint does go off. Apparently it can still be used when it smells stagnant (so I've been told) but I wouldn't.

Mick

[BobL]

To certain bacteria a can of paint is a free lunch, dinner and breakfast for many generations. The one that really gets me is the one that smells like sweaty feet! Yes you can use it and the smell does go as it dries but you may need a gas mask to put it on the walls!

[Tools]

The other thing I have noticed with paint is that when you go back to it in 12 months time, the tin will be rusted around the lip, and crap falls in to the paint when you open it. It was never like that when I was a lad..........

[Big Shed]

This has been an ongoing battle between paint companies and can manufacturers.

The cans for water based paint are made from tinplate roller coated with an epoxy based varnish, but sometimes the coating is really too thin. The other problem is that the rims are supposed to be stamped from the same coated tinplate, but half the time they use plain. Even when they use coated, the stamping process plays havoc with the coating.

To add to all this, the water based paints are brought to a fairly high pH, on the alkaline side, but over time the material used to get that high pH (ammonia or morpholine) evaporates and the pH gets lower and lower, thereby adding to the corrosion problem.

The rust in the can often changes the colour of light wall paint, so where the paint is to be kept for touch up purposes it pays to decant what is left in a well sealed plastic bucket type container.

[durwood]

All paints have a "life" so its not a bad idea to only buy enough for the job if thats possible though if you are like me you buy 4 litres as it only costs a few bucks more than 2 litres. Obviously it can be used for a time after you buy it but don't forget it may have been on a shelf in the factory or in a shop for a fair amount of time before you get it, especially if its a colour which is not popular. Always a good idea to buy from shop which has a large turn over.

The worst paints are polyurethanes ( had them go off in an unopen tin in less than 12 months) and air dry enamels. Lacquers last a lot longer some over ten years if sealed properly.

The latest auto water paints are now usually supplied in a plastic container, weirdest thing is they don't need to be stirred "ever". The are in a container with a small cap so its not possible to put stick in them to stir.

I think big sheds idea of decanting left over paint into a plastic container is a good one. I always keep the plastic containers that gyprock type products come in ( stud adhesive, jointing compounds etc) they are easy to clean out just let the dregs dry out and you can usually peel out the left overs and have a clean container. The donut shop in our shopping mall sells his 20 litre containers his flour mix comes in for a few bucks they make great paint or other stuff containers. I have one with the remains of a sand and cement mix bag in one.

[Slobba]

if you have added water to thin the paint and then put the left over paint back in the can...yep it will go off. if you use paint that has gone off in a dampish room..expect mould..i have seen 1 room in a house that looked like a vine creeper, because the painter used rotten paint..

i used today paint from a 20 ltr can that was last opened 7 years ago.. as long as the oil is covering the paint it will last for years....if it STINKS like a ferretts armpit DONT USE IT in damp areas.

flat acrylics seem to go off quicker, as it has less oils...

and also depends on where you store your left over paints

[Big Shed]

"Oils" in flat acrylics?

[Dave-Ben]

Paints are a mix of polymer - pure acrylic, styrene acrylic or vinyl acetate (VA)(for cheap paints such as ceiling paints) poly vinyl acetate (PVA) is the same as glue. Both these watre based paints will have bacteria or mould and fungi attack. VA based also have cellulose present. These are highly succeptable to mould and bacteria attack.

The paint companies have been regulated by "well meaning government regularions" to how much of some "biocides" which is added to kill bacteria they can use as some of these are hazardous. The best ones to kill the bugs are also more hazardous to humans.
If there is an attack by bacteria or mould etc, this then reduces how much is left to continue to attack until it is all consumed. About three years ago these had to be reduced to teh new regulations.
Bacteria attach will small more like rotten eggs.
Again Big Shed is right by decanting into smaller containers - either plastic or tins . You need to minimise the air space on the remaining paint. Often also inverting the cans will keep a wet seal around teh lid to prevent paints going off.

Oil based (Solvent type) also will go off - but this would involve them drying bacteria or mould will not survive in a solvent enviroment. Again if there is a large air space above teh paint it will dry. Single pack Urethane types are react with teh oxygen - that is how they cure.

So if teh paint 1. does not smell, 2 not solid. Once mixed it will be OK

reagrds Dave-Ben

[Slobba]

"Oils" in flat acrylics?

once settled you should see around 30mm in a 10ltr high grade flat acrylic...i use the term "OIL" as that is the term we painters call it...if i were a chemist i would be able to say exactly what it is

[rod1949]

The other thing I have noticed with paint is that when you go back to it in 12 months time, the tin will be rusted around the lip, and crap falls in to the paint when you open it. It was never like that when I was a lad..........

Cause we were splashing oils around with lead in um.

[micktb]

paints go off because of the water added in. buy only enough paint .work out the area to be painted use a non toxic paint like oikos solvent free paint system it is the real deal