We deal with sell-buy dates all the time in our homes. That milk container in the fridge says the sell-buy date was two weeks ago, so we wonder if that means the milk is bad and should be tossed. What do we do?
We smell it first, and if it smells bad or spoiled, we know the answer. If it smells okay, then we taste it. It seems okay, so it goes in our coffee
When it comes to wood stains, we go through the same exercise. We don’t remember exactly when we bought it or how long it’s been on the woodworking shop shelf. Most wood stain cans do not indicate a sell-buy date, so we’re at a disadvantage there. We open the can and look inside to smell it, just like we smelled the milk.
If an oil-based wood stain still smells like a wood stain, chances are it’s still good. Water-based stains, on the other hand, have a very mild smell when the can first opens, so if you don’t detect a strong smell, chances are it’s still good. In the smell test, then, if your oil-based stain smells like stain, go with it; if a water-based wood stain smells mild, go with it.
There’s more to know, though, so follow on.
Type of Stains
As we mentioned above, there are two types of stain: oil-based stain and water-based stain. Each will have its own shelf life, although generally, you will find it to be around 3 years unopened on your shelf before you want to test it first. You’ll find this on the can, or you can look it up on the product’s technical data sheet, discussed below.
We all know what a wood stain is, and we won’t go into too much detail here since we’ve done that before. They are similar to very thin oil or water-based paint. They are, actually, a type of paint used to color wood.
They contain a colorant that has been dissolved or suspended in a medium or solvent: in the case of oil-based stains, the medium is oil; in the case of water-based stains, it’s in water. They will seal off wood and offer water resistance to it, although they do not make the wood waterproof. The colorant will also offer protection from the sun’s UV rays since UV exposure can cause the wood to crack, warp, or cup.
Oil-based stains have good adhesion to the wood’s surface and offer a richness to the grain of the wood. They contain noxious chemicals, though, and VOCs (volatile organic compounds) that can be harmful to you. A respirator should be worn when working with an oil-based stain.
Water-based stains, on the other hand, contain no harmful chemicals and virtually no VOCs. They are easy to clean up after and offer resistance to mildew and mold. For those who are more eco-conscious in their shop, water-based stains offer a friendly alternative to oil-based stains.
Technical Data Sheets and Wood Stain
Each stain manufacturer publishes a Technical Data Sheet for their product. It generally includes:
- A description of the product
- Recommended uses
- How to prepare the wood surface for its use
- How to best apply
- Dry time
- Its physical properties
- Shelf life
- Flash point
All of this information is helpful, and please note the last two items on the list.
Shelf life will give a clue to help you in determining whether your stain might have gone bad. The flash point has to do with the temperature at which the product will ignite, a safety measure you want to pay attention to when storing and using stain.
As with just about everything else in the world, you can find the technical data sheet about your stain online. Manufacturers will include it as a resource on their websites, so that’s where you start. Of course, you can also simply “Google” the question about shelf life for your particular stain, too.
We’ve written about Varathane products in the past, as well as a mention here and there about General Finishes products. Each of these manufacturers publishes its TDS on its website, and we know that Minwax does the same. Be sure to look at your product’s website as the first point of reference in determining whether your stain has gone bad.
What To Look For To Determine If Your Wood Stain Has Gone Bad
If your shop records-keeping is detailed, you’ll have a record of when you purchased a can of stain. Some keep that information on their inventory sheet; others use the simple method of writing it on the cans of stain before they put it on the shelf. We use that simple method in our shop with a permanent marker on the bottom of the can where it won’t likely be covered by a drip or a spill.
Beyond that, the testing can continue.
The Nose Knows (maybe)
There is also the smell test we wrote of above. Oil-based stains will smell of wood stain if they are still good and usable, and if they do not, your testing will probably end there, and you’ll be off to the store for a new can. Water-based stains, on the other hand, have a mild smell, and anything stronger than a mild smell might spell the end of their use.
The smell test, though, is not absolutely determinative of its usefulness, though. There’s more.
If the texture of the stain has changed, that’s a bad sign. Visual examination will indicate whether the testing can stop at that. A liquid stain should still be a liquid (both oil stain and water stain are liquid), and a gel stain should still be a pudding-like consistency. If neither is the case, you might be in trouble.
If all you notice is that the pigment in the stain has fallen to the bottom of the can, give it a stir. In fact, stains should be stirred regularly when you are applying them, as falling pigment is common in wood stains. If a good stir restores the visual appearance of the stain, you might be fine.
The Drying Test
If you’ve gotten through the first steps in your testing but still have some doubt, use a little. Grab a piece of scrap wood and apply some of the stain. Let it sit for a few minutes, and wipe the excess stain off with a rag. Excess stain, by the way, will interfere with as even an application color as is possible based upon the stain and the wood.
Give it a day, and then feel the wood. Did the stain dry? If it is dry and did not come off on your hand as you rubbed it, the stain is usable; if it still feels wet, it needs to be disposed of safely and replaced with a new can.
Storage For Your Wood Stains
How and where your stain is stored can affect whether it will or has gone bad. An even and consistent environment and a minimum of air in the can if it has been opened can extend the shelf life of your stain beyond the generally accepted 3-year shelf life expectancy. If your shop has wide swings in temperature, though, it’s probably going to be that 3-year span. If the can has been opened, and the lid has not been replaced tightly, you might get a year or less after that opening, too.
Proper storage, then, is important for the life expectancy of your wood stains. In fact, proper storage and care are important for all shelf products and power tools, frankly.
The Testing List
Here are the steps to follow in a concise list that you can print and keep handy in your shop.
- Technical Data Sheet for your brand of stain for the shelf life.
- It should still smell like stain (oil-based) or have a mild aroma (water)
- It should not have separated or look different than it should for a wood stain (fallen pigment excepted)
- It should dry fully when tested over a 24-hour period
A failed test along the way will likely show itself in the next test on the list, too. Bad smell likely leads to something about the stain’s appearance, and both likely lead to a failed drying test.
While we like to include some video interest in our articles, on this one, words must suffice. We could not locate on-point videos. In its place, we offer the above-numbered list to keep handy in your shop if you ever have questions about your stains.
Show the same care in storing your stains and finishes as you do your power tools, and you won’t have to use the list and do the tests.