MDF


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I have been making nick-nack type items out of mdf board. I am using spray paint to cover them. My question is, how do I get the paint to hold on the edge... grain?!? While spraying up these items, the face edge takes the paint on quite well. I have sanded down the edges with 120 and then 400, so to me, the edge looks as dense and smooth as the face edges. The paint seems to soak in and then the edge color (brown) starts to bleed back through. I have even tried primer spray as a substrate to the actual paint layer.

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Yeah, its definitely a huge jump but MDF sort of disintegrates as you sand it with most any grit paper. I used 120 to knock down the valleys created by my bandsaw and 400 to knock down any potential sand marks from the 120. The 400 is gritty enough to put a chamfered edge on the project pieces to remove sharp edges with little sanding as is. once I finished with the 400 I ran my hand over it and thought "hmm, feels just like the face edge now" 

  Looks like the glue sizing could be the ticket. Thanks all

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Primer also works well. I used MDF for trim so i had to seal and paint a lot of mdf edges. 1-2 coats of primer and then 1-2 coats of paint. I never got everything covered well in 1 coat. The above glue thing might work as well i was always hesitant to add so much water to something that swells from water.

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I've found that glue size works better than any primer I've tried. But I mix it closer to half & half with water, maybe 2 glue to 3 water. Brush it on the edge generously & then a quick wipe with paper towel a minute later, before it gets tacky. I've never had a problem with swelling using this method.

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10 minutes ago, drzaius said:

I've found that glue size works better than any primer I've tried. But I mix it closer to half & half with water, maybe 2 glue to 3 water. Brush it on the edge generously & then a quick wipe with paper towel a minute later, before it gets tacky. I've never had a problem with swelling using this method.

I never tried it but that's mostly because i had 600 - 700 LF to get done and i wasn't about to experiment.

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Another use for glue size on MDF is hardening the edges of a template. I use very little water, maybe 70% glue 30% water and a disposable foam brush. Very thin coat to prevent swelling. Coat, sand repeat as needed. Keeps the edge from wearing/deforming from repeated use w pattern bit bearings.

A client had me cut 20 sheets of 1/2" MDF for a rush job in his upholstery shop . I ended up with 20 - 22" x 97" x 1/2" scraps. Great stuff for jigs & mock ups. It's what I'm using for the arch templates. If your in the Atlanta area holler if you want a piece or 2.

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