Can you mix older opened deck stain with new cans?

Mixing older opened deck stain with new cans is generally not recommended, as the older stain may have degraded or changed in consistency and color. This can lead to uneven application and unpredictable results. If you choose to mix them, ensure they are the same type and brand, and thoroughly stir the old stain to check for any separation or impurities. It's always best to test a small area first before committing to a larger application.