A: I will make an educated guess here. The only time I have seen such a chemical reaction is from combining 2 dissimilar chemicals, when the first one applied has not properly dried. I have seen this when a polyurethane is applied over lacquer sealers that have not dried. (I don't use such sealers myself.) If the stain is not actually dried, then when you apply the first coat of polyurethane, It can actually "pull" enough of the stain from the surface to make the color look lighter and blotchy. As a representative of a major stain and floor finish manufacturer recently said: "you finished product will only be as good as the first coat of finish". What he meant was that if proper drying has not occurred, It can spoil the rest of the job. Things such as the problem you mention, or the finish actually pealing from the floor surface, if not right away, then soon.
Related questions about refinishing and staining wood floors:
>Gloss, Satin, or Semi-Gloss?
>How long will it take me to sand my floors?
>How long would it take you to refinish, stain, and polyurethane...?
>Should I sand my own floors?
>How do I buff spots a pole sander can't reach?
>Is it possible to refinish engineered floors?
>Can I sand with nails in place? Can I recoat with a low gloss oil-based urethane?
>Do I have to sand the whole floor, then stain, then polyurethane?
>I was wondering if waxing the floor would be a good option to varnishing?
>Can a soft wood be sanded like a hardwood?
>Is it possible to have too many coats of urethane?
>Cost to resand 1400 sq. ft.?
>What do people charge for sanding and finishing natural (3 coats- No Sealers)?
>How much will it cost to refinish my hardwood floors?
>There is a living room, dining room, staircase and upstairs hallway, together with 4 small bedrooms which we would like to have done. Is this going to cost thousands of dollars or can it be done quite reasonably?
>If I fill some gaps *******, and the wood expands some during the summer, will that squeeze some of it out?
>Should finish be applied over filled nail holes?
> Is there a filler for filling the gaps between the planks? Should I punch the nails through and rescrew the planks to the joists before sanding? Do I apply the filler before I sand? What sealer should I use?
Finish Problems (e.g. Air Bubbles)
>What causes air bubbles?
>Did not buffing between coats cause this?
>We had the flooring company come back a second time tofill in some gaps and buff and put another coat on. We now have veryvisible air bubbles in our urethane finish (they were not present the first time). What is the best way to remove the air bubbles?
>I have two rooms. One is 9x12 the other 11x20. They are already stained with a royal mahogony minwax stain. It has a high gloss finish and the finish is now scratched and starting to peel. What do you suggest we do, strip and sand right down? What would the cost be approximately? How long would it take?
>At a doorway my urethane finish has lots of debris in it. How do I fix this?
>A contractor just finished installing/finishing my hardwood floors and left multiple lap marks (covering the entire width of the floor). What should be done about them?
>When there are air bubbles in the polyurethane finish, can you spot sand some of them by hand and then touch up that spot with another coat of polyurethane?
>There are some worn areas on our floor that need refinishing. Is it possible to redo only the worn areas andhave them blend into the older finished areas without redoing the entire floor?
>After many professional sanding and recoats, why is our floor is still rough?
>What do I do now that my finish is peeling off because there is wax in the grain?
>What do we do about problems with swirl marks in the floor finish?
>Why did the polyurethane peel right off?
>There always seems to be a film on the floor and they show all the dirt. Can I remove the 'shiny' top coat and redo with something more 'matte'?
>We have sanded off all the old stain, used the 120 grit to give a smoother finish, used a polyurethane but it still looks dull. I was reading on sanding tips and it says that after we sand the stain off, put the new stain on, then add the polyurethane, to sand it again lightly with a 120 grit and then add another coat of polyurethane for a smoother finish. Is that correct?
>We have put on 2 coats of water based polyurethane on our floors. The floor feels rough. How do you get that hard smooth finish?
>We have done the second coat of polyurethane but the floor is still rough and not shiny! What do we do now?
>The polyurethane coat on our hardwood flooring is peeling and flaking. I was able to scrape off most of the coat in one room. Should I apply wax or polyurethane?
>I just applied stain and poly. Why are my floors sticky?
>Why is my stain not drying faster?
>We stained our floors. Why are some areas lighter than the rest?
>Can a dark stain be stripped and stained to match lighter floors?
>Do I choose a wood putty to match the colour stain I use? Can I use a minwax-type gel stain that I have used on furniture, or do I need a special floor stain?
>Is there anything that I can do now to repair that blotchy appearance on the pine plank floors I just stained and refinished?
>What colour hardwood works best for a small room?
>How do I get the stain on my banister to look even and not blotchy?