Spraying Post-Catalyzed Primer
Advice on equipment and application methods for a high-viscosity, high-solids post-cat primer. June 17, 2009
Question
I was looking through some previous postings and I see that ML Campbell Clawlock primer is recommended for MDF surfaces. Reading through their product literature, the viscosity is given as 115-145 seconds in a Ford 4 cup. That's two minutes! Anything I've sprayed with my conversion guns has been four or more times thinner than that. What equipment is recommended for spraying this stuff?
Forum Responses
(Finishing Forum)
From contributor A:
Most people thin Clawlock. It is a very thick product out of the can.
From contributor B:
I have sprayed a lot of ML Campbell's claw lock and Magnaclaw undercoats and they are quite thick out of the can. I thin it down by 10 to 15 % and I find it sprays with ease. It also makes for easier sanding once dried.
From contributor G:
I thin it down 20% and spray it with a pressure cup gun. I could spray it at 10% but it doesn't flow out as well. For shaped surfaces on MDF I spray two coats sanding between, then I spray the whole item another two coats (sanding between) and get a nice even smooth finish.
From contributor I:
Are you saying that you spray four coats of Clawlock altogether?
From contributor G:
The thing that I spray most like that is the beveled edge of a panel on a door. The beveled edge does get a total of four coats. But the first two are knocked down pretty hard by sanding. This gets rid of the fuzzy edge from the MDF. Plus it is thinned out 20%. The rest of the door gets two coats including the face and back of the panel.
From contributor R:
I've sprayed many gallons of Clawlock with a Kremlin Airmix with no thinning and used the same tip as for spraying Duravar or Krysal. A little more pressure is needed, about 35 lb., pump 15 lb. air. It does a nice job.
From contributor T:
I found that reducing it up to 20% with their Flow Enhancer or nitrocellulose, spraying around 4 mill application, allowing proper dry time then re coating to desired build. My experience with this product has been very good. I prefer to use it as a prime coat on all my MDF projects. It wet sands like a dream too. It is also very tint-able base over it.
From the original questioner:
Well, it turned out to be pretty easy to work with. I bought an HVLP conversion gun with a 1.7mm nozzle set, and added about 20% lacquer thinner. The first coat required some light sanding, but the second coat looked just like a finish paint job, only completely flat black.
