Ok, I’m not going to actually say what the ‘best’ polyester primer is. Better yet, this post is about the factors that make a polyester primer good. It is important to be using high quality products, but a lot of times, it’s far more important to not abuse products, and just focus on doing great work. The question I’m asked the most, by far, is what polyester? Focusing on the work is probably more important than asking what brand is used. This is just a brief summary of things to pay attention to. I don’t like to say one brand in particular is great, always pay attention for yourself to what your spraying. If you notice something changes, do something about it
- Shrinking. The point of using polyester over urethane, is it barely shrinks. Some brands do shrink more than others though.
- Let any excess mixed polyester dry in a mixing cup, and keep it, and watch what it does. Some won’t shrink at all, some won’t for a few weeks, but after a few months it will slowly shrink a little bit. This is the best way to tell, by leaving 3-10 ounces left to dry.
- Adhession. I really haven’t come across a polyester that doesn’t stick well. Make sure the substrate it’s going on is clean and dust free. Spray the first coat a little lighter as a ‘tack coat’, and everything will be great.
- Heavy. Don’t abuse it! Just spray medium/wet coats. Don’t hammer the polyester on, it can crack.
- Baking. Let it air dry. If you want to bake it, which you should, do it after it’s cured. It dries fast enough and hot enough on its own, don’t throw extra heat on it.
- Metal. If you’re worried, use a light coat of epoxy over bare metal spots. Let it dry 36-48 hours, lightly sand the epoxy with 150, and then spray polyester. Epoxy must be full set before polyester goes on it. All in one products are not as good, there are always compromises.
- How it sands. Quality comes before how easy it is to sand. Sure, some sand better, but never use a lesser quality product just because it’s a little easier to sand. This should be on the bottom of your list of things to care about.
What do do I like?? Recently, I’ve used Standox, Glasurit, and Spies Hecker. Those threee seem to be very high quality products.