How to keep acrylic paints usable

I was looking for suitable color for one of my current projects when I realized I hadn't checked the acrylic paints for a couple of years. They are easy to keep usable, if only you remember to check them regularly.

The first thing to do is to get a bottle open. Usually it's enough to open the lid (the upper part of the top that covers the small hole on the top) to let some air in, if you can't get the top to turn. Once some air gets in, the top should turn more easily. If not, you can try using a kitchen towel to get a good grip. This time I had a couple of bottles really badly stuck, and I found out that the sort of cleaning pad shown in the next picture is quite useful. The rough side gives much better grip than a towel.

Once the bottle is open, take a long, thin stick. I use a screwdriver, because metal is easy and quick to clean before using it for the next color. Stir the paint to get an idea of how thick it is. If it looks normal, just stir well, close the bottle again and shake it a few times. If it's thick, add some water, close the bottle and shake vigorously to mix the paint and water. The amount of water depends on how much paint there is and how thick it is. You can add the water a little bit at first, shake, then check, and add more if needed.

If the grooves inside the top have a lot of dried paint in them, clean the inside before closing the bottle again. A screwdriver is good for this purpose as it is easy to scrape the paint away with it and its tip fits the small grooves.

If you've got bottles with so little paint left that it's not worth the trouble, you can clean the bottle and use it for mixing your own shades. In the first picture of this post, the second bottle from right is that kind. I remove the label to distinguish these bottles from original colors, and usually also write the purpose of the mixed color in the bottle, so I'll remember later why I mixed it.

To clean a bottle, put it and the top into warm water and let soak for a few hours. Then you should be able to remove the label easily. Rinse the bottle thoroughly, and if there is paint still left, fill it about half full, close it and shake well. This should remove at least some of the remaining paint. Repeat as many times as necessary. If paint is still stuck, let the bottle soak in warm water longer, overnight if necessary.

Removing the label tends to leave the bottle's sides a bit sticky, but that's just a nuisance, so I haven't tried to do anything about it. Solvent would remove the remaining glue, but I'm not sure what it would do to the plastic, so I just leave the bottles as they are.