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MDF and Agualente Plus Primer12/30
I have read many posts on priming MDF. I use MLC Agualente Primer and Agualente pigmented top coats.
I am having to shoot 3-4 coats, sometimes 5, of primer on raw MDF flat panels used in a maple door frame. I have tried everything when prepping MDF...from not sanding, to sanding to 400, and still, I always get raised fibers until after about 4 coats of primer. Iíve tried spraying light coats, back to back coats etc, and it all does the same thing. After each coat I light sand using 320, or 3M scuff pads so as not to cut too deep.
Perhaps a long shot, but is there ANY WB primer that wonít raise MDF fibers so much? I love how the Agualente Primer sands, but with so many coats, itís costing to much time. I used BIN shelllac for years, but would rather keep everything WB. I canít stand WB Bin primer as it doesnít sand well at all.
As a last resort, Iím considering switching to 1/4Ē panels of maple with MDF core just to alleviate so much fiber raising issues. I canít get the other types of MDF like Plum Creek in my location.
Thatís not normal. Are you using it out of the can? Thinning with water ?
If itís unsanded mdf faces you can use (1) coat. Itís a heavy bodied primer.
When we do raised panels itís a different story. Then itís sanding and BIN. Then prime the whole door with Aguelente.
We only use high quality mdf. Never sand mdf unless itís the core.
I switched to using Zinnser's shellac based primer on mdf to quit chasing the raised grain. 2 coats of shellac, one coat of General Finish white undercoat and 2 top coats of GF white poly for the front of doors and drawers.
Do you know if you're applying it at the right thickness, as in wet mils as recommended by the product data sheet? There's a wet mils thickness gauge you can use.
What MDF are you using? Standard or double refined?
Double refined (I use Plum Creek) MDF is far and above standard MDF. Paints much better, the profile cuts require no or minimal sanding before priming.
With the double refined MDF I do one coat of primer on the flat surface and on the beveled edge I just do a start coat on just the bevel and then a complete coat on all.
So there are two wet coats on the bevel and one on the field.
I am using a solvent base, but I would figure the coverage would be similar with waterborne.
Thanks for the responses guys.
I wish I could get the refined MDF like Plum Creek. As is, both of my main sheet goods suppliers only stocks the regular stuff, but the latest batch does look more coarse ..(larger fibers)..than usual. For me to get refined MDF will require buying a huge amount through my wholesaler. Everyone else in town outsources their doors and drawers, so apparently there isn't much demand locally for refined MDF.
In the past on MDF I used BIN Shellac, tons of Clawlock, and Vinyl sealer, and never had an issue. These days, for me, solvents in my locality are out due to insurance having gone through the roof, and a hard as heck to please county inspector and Fire Marshall.
I shot some more doors today and tried 2 light coats back to back, knocked down the raised fibers with 320. These two light coats helped a little, but not much. Still had to do three coats.
Normally, I spray a wet coat of 4 mils on wood, and often, one coat is all that is needed unless tannin is an issue.
I'm guessing it's the MDF. I went to the box store at lunch and got a 2x2 panel of whatever MDF they sell, and after one coat of primer I was ready to rock and roll with a top coat. No indication of what type of MDF it was on the label.
Will the white cabinet trend ever stop? lol.
Itís good that you figured out it was the mdf. I guess it gets confusing when you order mdf and they send you osb. 5 coats of primer later...
Aquaprime is excellent for this
Chemcraft aqua prime will help in this situation where you have to use junk mdf. it wont raise the grain less, but It will set up much harder, and a little faster than the agualente primer. I would imagine you will still have to do two or three coats and allow full dry time in between. It is not as thick as the Agualente primer.
If you do enough kitchens, and I don't think the white trend is going to fade anytime soon. You might as well go out and get a full bunk of the refined MDF. The time and money it will save you will be more than worth the initial cost.