Wood stains are known to remain in good condition for extended periods. But does wood stain go bad?
Wood stain does go bad. Generally, unopened wood stains tend to last longer than opened wood stains. This is because the seal in the paint can have been broken so it’s easier for contaminants to get in the paint.
On average, unopened wood stain can last over 3 years while opened wood stain doesn’t last up to a year. You should know that there are different types of wood stain, each with a distinct shelf life.
Also, moisture, heat, and storage conditions all affect the shelf life of wood stains. So a wood stain might expire sooner or later based on how it is stored.
Does Unopened Wood Stain Go Bad?
Unopened wood stain does go bad eventually though the stain can last over 3 years if stored correctly and left sealed. Just like every other product, stain will also go bad even if left unopened.
This is because the wood stain is made from a combination of solvent (usually water), colorants, and a binder. Over 85% of wood stain is made of colorants and water. There is no additive or special chemical included in the stain’s formula to preserve it. The only thing that keeps the stain from solidifying inside the can and from going bad is the solvent (or water).
However, water is easily affected by a change in temperature. A drop in temperature will easily make the solvent turn solid and colorants solidify inside the can. A high temperature can also cause the water to get hotter.
This will increase the heat leading to evaporation and steam build-up inside the can since the water vapor can’t go anywhere. This makes it easy for mold and bacteria to grow inside the paint can. So, even if you don’t open your wood stain, the nature of the solvent makes it possible for the paint to be ruined by temperature changes and moisture.
Also, sunlight and UV-rays can make the stain go bad even if unopened. This is because metal absorbs heat and since stain containers are made from metal, the temperature inside the container will be hotter. This can ruin the stain.
Does Wood Stain Go Bad After Opening?
Wood stain doesn’t go bad after opening but the shelf life of the stain is usually halved after the stain has been opened. This means if the stain was supposed to last 3 years, it wouldn’t last more than 18 months (or 1 1/2 years). There are different reasons for this.
The first reason is that when you open the stain container, the seal used to prevent contaminants from getting in is broken. So, it’s easier for contaminants like dust to get into the container.
However, you can seal the paint even after opening it by wrapping the lid with nylon or plastic wrap and shutting the lid tightly. This will prevent contaminants from getting in. But that’s only eliminating one problem.
For the second reason, there isn’t much you can do to prevent it. The second reason opened wood stain goes bad quickly is because of the weather and air circulation.
Immediately after you open the container of the stain, air rushes in the container. So while you mix and stir the stain, you are not just mixing wood stain but also air bubbles in the can.
These air bubbles become trapped inside the stain and even when you seal the stain lid, the air inside is enough to cause the stain to go bad sooner.
With air inside, the stain can begin to dry and can cure completely in weeks or months depending on how much air got in. This is why wood stains don’t last over a year in storage after being opened.
How Long is An Unopened Can of Stain Good For?
An unopened can of wood stain is good for up to 3 years. Generally, unopened stains last between 3 years and 5 years. Ordinary wood stains last for about 3 years at most while wood stains with sealants like varnish, polyurethane, and wax can last up to 5 years.
You should know that the storage conditions of the wood stain determine how long it will be good for.
If the wood stain is stored in cold and humid storage conditions, then it will not last up to a year. This is because moisture will affect not just the wood stain but the state of the container. The container can begin to rust and turn brown. This will lead to metal compounds dropping into the stain coating.
Also, it will cause leaking as moisture will get inside the stain. When this begins to happen, then the stain can’t last up to 6 months.
Also, if you store the stain at high temperatures, the heat will cause evaporation and build-up of steam leading to mold and bacteria growth in the container. But if the stain is stored correctly, it can last over 3 years. Here is a chart indicating the expected shelf life of different types of wood stains:
|Type Of Wood Stain||Expected Time To Last|
|Opened wood stain||1 Year – 18 months|
|Unopened wood stain||3 Years|
|Exterior wood stain||5-6 Years|
Less than 50% humidityYou should know that the chart above is subject to different storage conditions. The chart above was drawn based on the following storage conditions as indicated by manufacturers:
- Room temperature between 50-60 degrees Fahrenheit.
- Sealed stain container.
How To Revive Old Wood Stain?
There are a few ways to revive old wood stains. The method that will work depends on the type of wood stain you have and how long it’s been sitting in storage. The first method on the list is:
Method 1: Thinning The Stain
One common feature of all old stains is that they would have become hard and dull. This makes it very difficult to apply the stain as it will feel like you are trying to paint glue over a surface.
The old wood stain will be hard, stringy, and tough to mix. So you need to thin or make the stain lighter so it can be easily applied. To use this method, you’ll need:
- A paint thinner
- Paint mixer or turning stick
- A paint bucket
- A paintbrush
- Scissors (optional)
Here is how to thin old wood stain:
1. Empty the content into a paint bucket.
The first thing is to pour out the stain. You may need to cut the container with scissors to get a good opening especially if you are dealing with aerosol spray cans.
2. Add a paint thinner.
After pouring out the stain, add a thinning compound into the paint bucket. For oil-based stains, use mineral spirit, white spirit, or turpentine.
For water-based stains, use water or rubbing alcohol to thin the paint. Measure and add the paint thinner to the paint. You only need a small thinning compound. A good ratio to go by 1/4:1 (primer to stain).
3. Stir the stain
The next step is to stir the stain. You can use a turning stick for this if you prefer to do it manually or you can use a paint mixer. With a paint mixer, you are guaranteed a better result.
You should stir the stain for at least 5 minutes. For statin that is lumpy it hard, stir for 10 minutes. You should just stir to you get good flow and even paint color. This means you shouldn’t be able to tell the difference between the stain and the thinner.
4. Test the stain
After stirring, you should test the stain on a piece of cardboard or wall. If the stain goes on well, doesn’t streak or drip, and it gives a good finish when dry, then you have successfully revived the stain.
Another method is:
Method 2: Using Hot Water
This usually works for water-based stains. The trick is to add warm water to the stain and then stir vigorously till the stain is loose. This is a good method for frozen stains and clogged stains.
Other tips to help you revive old wood stains include:
- Mixing the stain
- Heating the stain for frozen stain
How Do You Know If Wood Stain Is Bad?
To know if the wood stain is bad, watch out for the following signs:
1. A Foul or Rancid Odor
This tells you that the stain has expired. The foul odor is caused by bacteria inside the stain that are eating and releasing gases inside the stain.
2. Swollen or Puffed Container
A swollen container is also caused by bacteria. The gasses being released inside the stain cause the container to become swollen or puffed. A puffed lid is another sign similar to this. A puffed lid can also be caused by UV rays from the sun.
3. Mold Growth on The Can
If you can see mold growing on the lid or inside the stain container, the stain has gone bad.
4. Hard and Stringy Stain
If the stain is strong or too hard to mix, it has likely gone bad. If the stain appears stringy, then it might have been affected by heat. However, when the stain is hard and stringy, it can be revived.
5. Texture Change
A change in the form or texture of the paint is an indication that it has gone bad. If the stain is gel or wax, it should appear gummy or soft.
If the stain is ordinary water-based or oil-based, then it should have a liquid form. If the stain has changed texture from what it’s meant to be, then it has gone bad.
How Long Does Exterior Wood Stain Last?
Exterior wood stain lasts between 3 years and 5 years if left unopened. Opened exterior wood stain doesn’t usually last more than 1 year.
Exterior wood stains tend to last longer because these stains are designed with preservatives and paint chemicals to preserve the paint and the finish when it dries from UV rays and moisture.
For instance, exterior polyurethane designed for exterior wood contains UV blockers and thermoplastics. These chemicals make the stain more resistant to temperature changes while in storage. So a can of unopened exterior polyurethane can last up to 5 years in storage.
However, just like other wood stains, if the exterior wood stain has been opened, it wouldn’t last up to a year. Opened exterior wood stains aren’t known to last over 10 months. This is because the chemicals in the stain react quickly with the atmosphere. You should know that 2-part wood stains don’t last more than 48 hours after being mixed.
Can You Use Old Wood Stain?
You can use old wood stain as long as you revive the stain first. Old wood stain is bound to have developed lumps and a few other imperfections. The paint will have also become dull and hard having being stored for months.
So before you can use an old wood stain, you need to revive the stain. This means you need to make the stain have a good flow again.
Overall, wood stain does go bad but you can prolong the shelf life of your wood stain by storing it properly and in the right storage conditions.
For unopened wood stain, store in a cool and dry place. For opened wood stains, ensure to seal the container before storing the stain and make sure to use it before 10 months.