If you feel anything at all then break up the clumps and see If your mass mixes back in with the overall consistency from the stain. If it dissolves in to the stain you can use it. If it stays lumpy the stain has separated and it's no good. Now http://deck-staining-concord-nc03135.blue-blogs.com/3237602/the-main-principles-of-concord-residentialpainting-contractors-deck-painting-concord-north-carolina