We just had a new kitchen put into our 1850's home, with period-style cabinets.

The finish we chose for the cabinets was 2 coats of milk paint topped with 1 coat of satin polyurethane. It was an oil-based quick drying polyurethane.

The sample boards we prepared with this combination seemed impervious to oil and water stains (although the milk paint alone was quite vulnerable to stains before the poly was applied).

Approximately one week after the poly went on and the kitchen was completed, we noticed a series of stains on the side of one cabinet. We do not believe that these stains were there a few days ago, although no one recalls spilling anything on this cabinet.

Water does seem to bead up on this board, so we don't think that the contractor forgot to put poly on this board, though it is possible.

Is it possible that the poly has not fully cured/set yet?

Any thoughts on getting the stains out? We tried dishwashing liquid, a paste of baking soda, a paper bag and heat, etc, per internet suggestions.

Note that the photo is rotated improperly--this is a vertical surface on the side of a cabinet, so it's difficult to let anything "soak" in there.

Help!