Fish eye is a term that describes the ridging or cratering of a newly applied finish; the finish refuses to lay down flat. Fish eye is common during refinishing because it is caused by the low-surface-tension silicone oil contained in many furniture polishes getting through the deteriorated original finish and into the wood.
There are two easy ways to test stripped wood to determine if you may have a fish-eye problem. If you are staining the wood, apply a wet coat of stain. If you aren’t staining, apply a wet coat of mineral spirits if you intend to use a solvent finish, or a wet coat of water if you’re going to use a water-based finish.
If there is silicone contamination in the wood, the stain, mineral spirits or water will bunch up into ridges or craters wherever there is silicone, and you will know that you need to take precautions against the contamination.