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In My Experience: What Additives Do You Use?

30 March, 2023


Jason Badger 
Kodiak Cabinet Refinishing and Painting 
La Porte, Texas 

The simplest thing you can do is add water, although it would probably be a little bit better to use a retarder. Technically, when you use water, you are thinning out the coating, so you are diluting the solid content. But the scale of which you do it is very minor, while the retarder, being an actual chemical, doesn’t take away from the solid content. Now, will you really notice that with a human eye? Probably not. 

If I ever add water, it’s very minor. If I have a full PPS cup —750 milliliters — at the most I'll add around 40 milliliters of water in there, basically just enough to help counteract the effect of having a lot of catalyst in your coating. If it’s hot and humid outside, you need it to help thin it a little bit and slow down that instant drying effect. The water really plays to your temperature and humidity, which is something I really have to pay attention to where I live in the Houston area because we get really hot and humid. Oddly enough, coatings like Renner really love heat and humidity, so they can dry and set up and flash off really fast. The water helps counteract that and helps you work with it a little bit longer, helps it spray with a little bit better flow out of the gun, hit the surface and level out a little better. 

I also add a lot of catalyst to the primer — it’s like super charging it. It helps with adhesion, chemical resistance and water resistance; it hardens the coating and helps it with resistance to scratches and marring. It’s really a great additive. The only disadvantage, of course, is it makes the coating have a pot life, and you have to know how to work with that. You’re usually going to need to use it within about an hour, because it does start to harden and gel up. But even if the pot life is four hours, there’s really no need to ever keep it in your gun past when you’re done spraying. 

One really good thing about the catalyst is that it helps with tannin and dye migration in woods — oak especially being the notorious one for tannins bleeding through. So if you have issues like that, then you add your catalyst to your primer, spray it on and let it sit for four to six hours, sometimes even eight. Usually, if I’m having any problems with that or think I’m going to, then I plan it to where I’m going to spray it toward the evening and let it sit all night. 

Sometimes you might see the tannins or the dyes or whatever still bleed through, and you’ll see them in that first coat of primer. But what’s cool about it when it’s catalyzed — don’t freak out because of what that catalyst is doing is while the tannin might be coming through — that catalyzing effect is locking those tannins in. 


Paul Freeman 
Blue Ridge Finishing 
Watertown, New York 

It’s basically by feeling and experience. If it’s 85 degrees and you have 60% humidity and you start brushing a poly or a varnish, a lot of time it’s going to drag, just like with old oil-based paint. I use a lot of Penetrol — that’s probably what I use the most. It depends on the conditions. I’ll use it if it’s really cold or really humid. I also use a lot of paint thinners to thin down the coating just a bit to give them a little bit more open time. 

Penetrol works really well because it’s more of a conditioner. I would use  versus the first coat, because I want that first coat to sink into the material. I just use regular mineral spirits and paint thinner on the first coat, and I’ll cut it maybe 20% or 30%. At that point, it’s real sloppy, but you just want to get your coating into this material as best you can. It’s going to raise the grain, but you’re going to knock it all down anyway. 

It’s so important to knock it down before you start applying your next coat. I usually use 180 grit — I wipe it all down and vacuum it. Then, I might use the 320 on the second coat as well as the final coat. Sometimes I use steel wool as a buffer, then just get the best natural hair brush I’ve got and lay it right in there. Oh man, it comes out nice! 

So it’s a process. It’s not only the material and how much I cut it — it’s actually doing it, watching every stroke, how to lay it off, and how not to leave drips, sags and runs. 

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