I have ran into this conundrum with partial bottles of nail polish since I was 10 years old. Some of the bottles were so old, they were thick, globby, and unusable. I did find a solution or two to take care of partial and unusable bottles of nail polish.
What to do with the partial bottle of nail polish?
Below are three ideas for using those partial bottles of nail polish laying around the house.
Mixing the bottles.
I have poured like and similar colors together to create a new color. This method does not always result in the best colors. It does sometimes have a better result than expected.
When pouring one bottle of nail polish into another, it is best to lay down a piece of newspaper or wax paper as your drop cloth. By doing this, any spills or drops will hit the paper covering the furniture or cabinet underneath.
I found using a lighter tone of another brand of the same color can lighten the darker color. Not all brands of nail polish are of the same dye lot. For instance, Loreal may have a darker shade of the darkest shade of red than Revlon.
After getting as much of the polish out of the one bottle I was going to throw away, I put the lid on the other bottle and shook until well mixed.
Mixing the colors in a lid from a jar.
I found another way to mix the colors was to drop a few drops of one color into a washed jar lid with another color and mix with a toothpick. By doing this, I found if I did not like the mixture of colors, I would not mix the two bottles together. Also, if I had fuller bottles of nail polish and wanted to have a new color, this was the best way to do it. On occasion, I would find I would have a swirled mix of colors that looked good together and painted my nails with that test sample.
Mixing the colors on your nails.
With this method it is best to test it on your toes first. Take the darkest color in your collection and paint your toenail.
I have found letting this color dry before applying the next coat of a different color. When applying the next color, it will need to be a shade lighter, preferably with a bit of transparency. For example, if you have a maroon base coat, a pink pearl color will go nicely over the base coat.
The same idea can be used with a clear coat of nail polish. The clear coat will often lighten the darkest nail polish slightly.
What to do with unusable bottles of nail polish?
When I found a bottle of nail polish that was too thick, I would add a little nail polish remover to the bottle. By doing this it would thin the polish down to a usable amount.
When adding the remover to the polish, it is best to do it over the sink rather than newspaper. Any remover that does not go into the polish bottle will go down the drain. When using newspaper, the remover leaks through onto the surface being used.
Once the remover was in the bottle, I put the lid back on and shook as hard as I could to mix. Then I would check to see if it was thin enough to use. If it wasn’t I added just a few more drops until it was thin again.
If the bottle of polish is dried out, the remover method will not work.