7. Find dried glue
Dried glue causes spotting when you apply a stain or finish.
Most glue dries clear, though, so how can you tell where
it is? Water or mineral spirits reveal all.
Before a final sanding, wet the entire surface with water
or, if you have adequate ventilation, with mineral spirits. This
will make the wood darker, but glue drips, spills and fingerprints
will be easily identifiable because they’ll appear as a
light color. How does this work? Glue seals the wood’s surface.
Water or mineral spirits won’t penetrate the glue spots,
so those spots won’t become as dark as the rest of the wood.
Water will soften dried glue, making it easier to remove
with a card scraper or a chisel. You can also wash off glue by
scrubbing with a rag and hot water. When you’ve removed
the glue, sand with the highest grit of sandpaper you used
on the rest of the project.