HDU Primer Question

[James Stirling]

We are having some problems with Coastal water based primer and HDU. Unless forced into the surface with brush or squeegee, it doesn't seem to bond. This is even with time to cure.

So, what are you guys and gals using to prime HDU and how are you applying it? Or, what might we be doing wrong?

Thanks, James

[Mark Summers]

I'm assuming the problem is the lack of adhesion. This took me awhile
to get this one dialed in. I use Signfoam 18#. Pretty dense cells here.

I was' just putting my XIM- UMA water base primer directly to the
Signfoam. I was getting chunks of primer/enamel coming off when I
peeled off the Anchor Continental #117 (med.) sandblast tape.

Now I hand sand the piece with a pretty coarse piece of sandpaper,
air-blow the piece real good and proceed to apply 4 coats of XIM.
I've had pretty good succes doing this. Hope this helps.
Give us specifics, materials brand etc. for further help.

Mark

[Dan Seese]

James,
I've used both the Costal Enterprises FSC water based high build primer as well as the Sign Foam primer - Sign Prime. I like them both because they fill the pores and sand so well. You can build it up and then sand, taking care not to sand down to to the HDU surface. My preference is the Costal Enterprises product but I need to thin it first because I usually spray it.
I've also tried both Jay Cooke & Chromatic but hated both of them because they sand so poorly - a lot of balling-up.
I think the key with HDU is to eliminate all dust before painting or priming. This can be done either by blowing it off or by rinsing the surface well. I've not had adhesion problems when I do this.
Hope this helps.

[James Stirling]

We use 15# or 18# Precision Board and the problem is with adhesion with the Coastal Primer. We blow off the foam and sometimes rinse it. Somewhere we were given the impression that we were not to thin the Coastal. Sounds like that is mistaken.

James

[Raymond Chapman]

We've never had a problem with the Coastal Primer/filler in all the years we've been using it...but then we don't paint and then apply sandblast mask. Our procedure is to apply the mask directly to the unprimed HDU, blast, and then paint everything.

Now, we just put it into our ShopBot router and don't worry about mask or sandblasting.

As said earlier, the solution to most problems is removing the dust. This is best done with high pressure water and you don't get a bunch of dust all over everything.

Thinning the Coastal should not create problems. We have brushed, sprayed, and rolled both thinned and unthinned with good results.

[Bill Masters]

I have been useing a latex stain killer called Grip and Seal from Coronado, cost about $30.00 a gallon. Also use it as a primer for vinyl banners that I have made from old billboard flex faces, sticks tight and stays flexable.