I am redoing an 1890's victorian and have just finished painting the living room. To protect the mantle I removed it and then plastered and painted. I also redid the woodwork with sealcoat and it worked great. I then tried it on the mantle, and it worked great everywhere except on the top surface. There were many areas of crazing. I attacked them with fine sandpaper and steel wool and got a nice clean surface and stained the light spots where I got a bit too enthusiastic in my sanding. I wiped it all down and left it for a day and tried another coast of sealcoat and got the same problem:

Here is another view:



And another:



I am trying to get the living room done this weekend. What am I doing wrong? Or what can I do to fix this crazy crazing problem??