I have a window sill thats made from MDF and the way it was fascined is with counter sinked screws they were pudded over with painters puddy and sanded.I put a coat of primer on them but I can see were the puddy was applied,like an outline of a button coming thru .Does anyone know the remedy to get rid of the buttons.Thanks mbill
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mbill
If you didn't lightly sand b/4 you applied the filler, you likely have a slightly higher halo showing up on the surface of the mdf. MDF has a tendancy to puff up when nailed or drilled.
Use sandpaper wrapped around a block of wood to flatten out the surface. I'd use a harder filler like Durabond (a powdered joint compound) to fill the hole (because I always have it on hand-you can get a smaller amount in something like Durhams Rock Hard Water Putty).. Apply to pack the countersink and a flat smooth excess around it (Use a wider knife-3"). Now when you use the block and sandpaper you'll sand perfectly flat, but stop b/4 you expose the outline of the countersink. You don't want it to appear as a hump either.
In your case, I'd dig out the softer filler and go about it as above.
BTW, mdf is not a good choice for a window sill as moisture is always a possibility in that area. Hope that you sealed ALL surfaces of it b/4 install. Also, coat well. And keep it pristine-any knicks that see water will swell up like a poisonous toad.