What happened to this skirting board?

[diynewb878]

Just started painting new skirting boards (15mm MDF). I used an all-purpose primer first, and just started the first eggshell white coat. Does anyone know why I’m getting the effect below?

 

[KenGMac]

Looks like there may be some sort of "reaction" between the two paints?

Were the two paints from the same maker?

Ken

 

[Deleted member 174758]

The MDF surface may have been contaminated with something like silicone or possibly release oil from the pressing process. Flat back, give it a coat if Zinsser BIN or of a pre mixed white dewaxed French polish and you should be able to.reprime

 

[Sunshine32]

I agree with the previous two posters.

If it were me, I would strip as much paint off as possible, lightly sand and I mean lightly as MDF is not very tolerant of sanding and apply Zinsser Bin primer. Hoping you are applying an oil based paint as the final coat though as BIN does better with oil based paints.

 

[Rhothgar]

Agree. Zinnser is the answer to the Universe!