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blackrose

Paint shelf life

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I was speaking to Hemple on the phone today to find out if I could use a single pack polyurethane top coat on top of their Epoxy Primer/Undercoat. The cans of epoxy are pretty old, in fact it's now called Hemple Light Primer. So the guy on the phone told me it was likely to be out of date because the hardener is organic and only has a shelf life of a few years at best. 

 

This made me wonder about other paints in my collection. What sort of shelf life does a single pack polyurethane topcoat paint have for example? Also I've been using a single pack Hemple Primer Undercoat between Jotamastic 87 epoxy on my decks and international Interdeck topcoat. The cans of primer undercoat are probably 6 years old but the paint's been fine. If it was out of date how would I know? None of the cans have any dates on them.

 

Perhaps Dr Bob has some knowledge?

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I’ve got tins of International  Toplac that are ten years or more old.  Sometimes have to cut the skin off, but otherwise it’s fine.

 

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58 minutes ago, dor said:

I’ve got tins of International  Toplac that are ten years or more old.  Sometimes have to cut the skin off, but otherwise it’s fine.

 

 

Yes, some of my tins of paint are pretty old too. I find the skin forms only after the headspace in the can has reached a certain volume. It's probably temperature related too.

Edited by blackrose

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1 hour ago, dor said:

I’ve got tins of International  Toplac that are ten years or more old.  Sometimes have to cut the skin off, but otherwise it’s fine.

 

 

If you store the tins of used paint upside down, you will find that the skin has formed on the bottom when you turn the tin the right way up to open it.

 

Just be careful not to pierce the skin when stirring the paint.

Edited by cuthound
Spillung

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6 minutes ago, cuthound said:

 

If you store the tins of used paint upside down, you will find that the skin has formed on the bottom when you turn the tin the right way up to open it.

 

Just be careful not to pierce the skin when stirring the paint.

 

Good tip but it must be quite difficult not to pierce the skin while stirring? I always give my paint a really good stir to get it all mixed properly. Also don't you get lots of the settled solids stuck to the lid when you open it which are then difficult to stir back in?

Edited by blackrose

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1 hour ago, system 4-50 said:

The older the paint the more likely it is to be real paint...

 

Mmm... Not according to Hemple's technical dept.

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40 minutes ago, Cheshire cat said:

Put some clean stones in to displace the air before you put the top on.

 

You'd have to put a lot of stones in to displace half a can of paint and then a lot of the paint would be inaccessible below the height of the stones. It sounds messy. I'd rather just cut the skin off.

 

Anyway thanks but let's keep this on topic on paint shelf life if anyone knows?

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I'm in the 'store the can upside down' school.'  My tunnel band ? Is cream and the Masons paint for that, a 2.5 pint tin is about 20 years old. I used it a few months ago and it was fine. I always take shelf life dates with a pinch of salt.

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I have recently been using  various Sherwin-Williams 2 part epoxy paints. They all had a date code on and all pretty much past their  use by date as recommended by the manufacturer. The oldest paint definitely takes longer to cure and in an  extreme case was several weeks. They did however all set ok in the end. Most of the slow curing was noticed with the primer paints, top coats seem to be much better.These two part  paints do not skin over in the tin.

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The hardener in a 2 pack system can degrade so will not be as good at crosslinking the coating, hence shelf life is important.

For single pack systems, most cure with air or moisture and the base polymers that the air activates do not really deteriorate. The skin is the cured paint. If it's still runny underneath and The viscosity still good then the paint will probably be reasonable.

Single pack polyurethanes or siloxanes may age a bit more than the old alkyd type paints so if they are too thick then dump them. If not, likely ok to use.

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19 minutes ago, Dr Bob said:

The hardener in a 2 pack system can degrade so will not be as good at crosslinking the coating, hence shelf life is important.

For single pack systems, most cure with air or moisture and the base polymers that the air activates do not really deteriorate. The skin is the cured paint. If it's still runny underneath and The viscosity still good then the paint will probably be reasonable.

Single pack polyurethanes or siloxanes may age a bit more than the old alkyd type paints so if they are too thick then dump them. If not, likely ok to use.

 

Thanks. It sounds like the main issue is with epoxies rather than single part paints. I'm going to do a test patch with the old Hemple epoxy primer/undercoat, give it 24 hours and see if it's still any good.

1 minute ago, ditchcrawler said:

I decant mine into 250 and 125 ml cans so they are almost full most of the time

 

I thought about that but new empty cans are expensive on eBay. Where do you get them? I'm not going to start washing out old cans with thinners.

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I clean and save glass jars with screw seal lids for this purpose.  Honey jars, chutney jars ect. If I have paint left in tins I stir and transfer to jars, up to the brim and screw the lid on tight and label them. For small amounts, glass fish paste glass jars.

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4 hours ago, bizzard said:

I clean and save glass jars with screw seal lids for this purpose.  Honey jars, chutney jars ect. If I have paint left in tins I stir and transfer to jars, up to the brim and screw the lid on tight and label them. For small amounts, glass fish paste glass jars.

 

Shippam's fish paste. Does anyone still buy that stuff? I bet you still eat spam too! 

4 hours ago, Jen-in-Wellies said:

Been using tins of ten year old Craftmaster paint in between the showers over the last few weeks. Still fine.

 

Yes it's the two part paints where shelf life seems to be important. Not an issue for most single part paints.

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I use plastic washing up bottles. Squeeze the paint up to the outlet, clip on the cover and all good with no air inside to crisp up the paint or varnish.

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1 hour ago, Old Son said:

I use plastic washing up bottles. Squeeze the paint up to the outlet, clip on the cover and all good with no air inside to crisp up the paint or varnish.

 

Go on admit it, you used to watch Blue Peter didn't you. 😁

 

 

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3 hours ago, Old Son said:

I use plastic washing up bottles. Squeeze the paint up to the outlet, clip on the cover and all good with no air inside to crisp up the paint or varnish.

 

I never put paint in plastic containers for long term storage. I tried it once and the paint dried out pretty quickly. All plastics have oxygen and water vapour transmission rates, the rate at which oxygen (and other gases) and water vapour will permeate thrush them. It's a function of the particular permeant, the polymer, the thickness of the plastic and temperature & humidity.

 

Vapours of solvent based paint will permeate through the plastic over time. That's why paint generally comes in metal cans. Some water based paint comes in thick plastic cans but they will have tested the WVTR of the can and made sure it's minimal. I might be wrong but I don't think any solvent based paints are packaged in plastic? If they are it will be a thick high barrier plastic, not a thin plastic like a washing up bottle. I buy those big 1 litre plastic yogurt buckets with handles you get these days. They make great paint buckets if you don't want to carry a 2.5 litre tin while you're painting. But when I put the lid on one with paint in and stored it in a locker it dried out within a couple of months. It was quite hot in the locker which didn't help, but the paint in cans in there was all fine. Storing paint in glass with metal lids is fine but I don't want lots of glass jars in my paint locker.

Edited by blackrose

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I use Lidl jam jars. They have a good screw top seal.

Fill them with paint and a drop of thinners on top. Even if you can't get the lids off after its easy to pierce them to pour the paint into a paint kettle.

Everybody does use a paint kettle don't they?

I like the stone idea.

 

Chucking the skin away will alter the shade and make up of the paint I would think.

Edited by hider

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17 minutes ago, hider said:

 

Chucking the skin away will alter the shade and make up of the paint I would think.

 

That would be fairly insignificant I would have thought.

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46 minutes ago, hider said:

 

I like the stone idea.

 

Chucking the skin away will alter the shade and make up of the paint I would think.

Stone paint kettles, are you a reincarnation?😁

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7 hours ago, blackrose said:

 

Shippam's fish paste. Does anyone still buy that stuff? I bet you still eat spam too! 

 

Yes it's the two part paints where shelf life seems to be important. Not an issue for most single part paints.

The crab paste in little jars is lovely and makes a nice little snack spread on little water biscuits when I take afternoon tea. Spam fritters are tasty too.

The skin on a lice pudding preserves it for quite a while.

Edited by bizzard

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