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I have several buckets of four-year old latex paint leftover from finishing our basement. Many are still in unopened original containers, in particular, our primary wall paint.

I opened one to use for wall patching and found it to be completely separated. This bucket was also in the garage and was subjected to freezing temperatures.

With just a little bit of stirring it seems to be back to life, but I just want to be sure that I won't have any adverse affects using it to patch several chips and scuffs around the house.

How long is the shelf life for latex paint?

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From what I have read it varies with the quality of the paint and the storage conditions,but 3-5 years is reasonable for unopened cans. Most of the evidence seems anecdotal. There always seems to be a case of someone using something 20 years old that they got for free and it lasted 30 years. There doesn't seem to be hard evidence from manufacturers saying that you will decrease service life by X number of years if stored for X number of months.I would do a test sample on something similar to your planned use, wood trim,drywall etc. Give it a day or so to see how the color match and texture looks. If it looks OK you have nothing to loose. If you buy new paint you will probable want to redo the whole wall so it will blend in. If the old paint doesn't match you'll have to redo the wall anyway

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3-5 years seems resonable. We've been working off a 5 gallon bucket of trim color here and it's still going strong at 6 years and about a gallon and a half that we've put in smaller tins. Just make sure you stir very well every time you use it. One of the problems you will have with old paint in gallons is that the metal can rust throwing nasty iron oxide flakes that ruin the color. Newer gallons are plastic except for the lid which can rust if it gets a pinhole in the coating. – Fiasco Labs Sep 16 '12 at 23:27

For most finishes in indoor situations, I rely on a practical test:

Get a small sample of whatever you're going to apply it to. Prepare that sample as you would normally.

Open the finish. Stir it thoroughly (but avoid mixing air into it), getting ALL the solids back into suspension. If it seems unreasonably thick, add small amounts of the appropriate solvent (water, for latex paint) until it's back to a workable consistency.

Apply the finish to the sample.

Give it a reasonable amount of time to dry. (Check the label.)

After that, if it's still sticky, or if it rubs/peels off, or otherwise doesn't behave as you expected it to, chuck it. If it gave you a clean, hard finish on the sample, and you like the look of it, you can probably go ahead and use it.

I've used decade-old (at least!) latex paint left over from a prior owner to touch up around the house. Outside of the problem of the can sometimes having rusted into the paint (added iron oxide pigment, not well distributed?), it's generally worked reasonably well. I wouldn't use it on something I was building for someone else, but for my own place... hey, worst comes to worst I get a new can and paint over it.

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I just called Valspar customer service and they said latex paint shelf life is about 8 years if kept in "climate controlled" environment. I asked if that meant indoors, and she said yes, so 70 to 80 F. I asked what happened after 8 years and she said if moisture intrudes the paint can get lumpy. I think if a series of questions is asked of several manufacturers and the data is all added together, one might arrive at a reasonable answer.

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Paint is a chemical compound. It is formulated much like an adhesive so it sticks to what you paint.

Paint also has a carrier. Latex paint uses water. Oil base paints use mineral oil.

Chemical and physical reactions occur when you apply the paint. Most of the physical reaction is simply the carrier evaporating. The chemical reactions are the adhesives in the paint bonding together and with the surface it's applied to.

From the time it is made, the chemical reations in the paint slowly begin. If you let the unopened can sit long enough, the adhesive chemicals, solids and colors will settle to the bottom and solidify. If you catch it early enough before it completely solidifies and it is a gunk, you can mix it up and think you have good paint. You won't. Most if the adhesive qualities have been consumed making the gunk in the bottom of the can. It will not stick well to whatever you are painting.

Shelf life varies greatly based on a large number of factors, type of paint, temperature, color, etc.

Two years stored in good conditions is typically my limit, however I just threw away two gallons if one year old Kilz because I didn't like the way it mixed. It was the base coat on a remodel job and I didn't want to take a chance.

And I didn't just throw it in the garbage. I mixed it with the cheapest kitty litter I could find.

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IF there are any volatile compounds in the paint that are important to its adhesion properties, then you would want to keep as much of them in the can as possible. Therefore I suggest that you shake the can as much as possible before opening, then stir. This will help keep as much of the freshness as possible.

I've heard that paint stores will re-shake cans of paint that you bought from them. It can't hurt to ask if you are nearby.

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I just redid our walls with 16 year old latex eggshell paint stored in it's original can in our basement. It had been stored upside-down and was in fine condition. I put it into another container and used my electric beaters, mixing it with just a touch of water and it worked well. Now I'm wondering what I can put the bit that's still left into and keep it for another while in case it's needed for touch-ups, maybe an upside-down plastic jar with plastic wrap in the seal?

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Hello, and welcome to Stack Exchange. Your first couple of sentences was a good answer, but the last sounded like a new question; you may want to edit it out and submit it as a new question, otherwise you won't get any answers. – Daniel Griscom Jun 1 at 21:26

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