sealing mdf for painting

[myxpykalix]

is the best method of sealing mdf for painting a mix of 50% titebond 50% water? Would i still need to prime?

[navigator7]

is the best method of sealing mdf for painting a mix of 50% titebond 50% water? Would i still need to prime?

I dunno what the answer is Jack but see if my experience helps?
Yesterday, I was doing some MDF trim indoors.
I found a wet rag will remove the existing primer on the board! You can wipe the paint right off. Had no idea.
4 years ago, I made some MDF shutters for our house knowing full well MDF is for interior stuff.
I only did that because 19 years ago in rainy Seattle I knew nothing about MDF except that smooth white board was really appealing ... No sanding. I made MDF shutters with little hearts in them. They remain as good today as the day I built them despite two subsequent owners.

I used two coats of outdoor primer and paint and have seen that system work in extreme wetness and extreme heat and cold. Works fine. I'd do it again.
HTH

[bob_s]

Jack
I like the titebond method and then sand with 320
if you see any areas that look "open" recoat them and resand
I use water based finishes so I cannot use the lacquer based primer that some others use so I have found this to be the best alternative
don't clean the surface with compressed air after sanding as the fine dust seems tohelp smooth it. I just wipe it well with a dry cloth

[kubotaman]

I have painted MDF lots of times. I would recommend priming with Zinsser primer( brown label) which is oil base. You can thin it by adding Naptha which is a very quick drying thinner. Two coats on the machined edges should be sufficient but I always use more since I am very particular. This primer is exterior so that is not a worry. Best primer I have used and you can recoat with water base if you want. Sand with 220 grit and you will be surprised at your results. It sands extremely easy, just like chalk and has a very high build property. You can get results like a piano if you want. I have numerous times! Be sure to let it dry overnite so the sanding is easier. You can coat in the morning and then later that nite if need be. Don't sand between coats since this will remove your build up coat. One final sanding is all that is needed. If you find it a little hard to sand then that will indicate that it is not completely dry. I use it all the time and have very good results.

[wberminio]

Dido on Daryl's comments!

[pappybaynes]

It doesn't have to be the oil based Zinsser, the latex works just fine and will not wipe off.

[kubotaman]

Yes you can use the water base Zinsser but it doesn't chalk nearly as well as the oil base. That is why I don't use it.

[myxpykalix]

The mdf is part of the accents going on a castle bed for a little girl who has had brain operations and i think i'd rather stay away from oil based primer/naptha/thinners if possible.

I think Joe or someone recommended a mix of 50% yellow glue/50% water and that seemed less caustic to me.