As enthusiasts, everyone in the car audio world loves to discuss and argue about products, cars, installs, techniques, competitors and anything else that will carry a thread on an Internet forum. The problem is when we can't separate opinion from fact. With Internet forums especially, confusion reigns since the ratio is probably 80 percent opinion to 20 percent fact (my opinion, proving that nobody is immune).
I need to clear up some wildly spreading confusion about something that my staff is credited with inventing: The polycrete mixture that we use in our Phase X Advanced Techniques electives class is not the same as the "Polycrete" that was available from LePages Adhesives at one time. They still make Poly Stipple, Poly Filla and other residential crack fillers, but the material we formulated for car audio installation is totally different from anything you can buy at Home Depot.
The "Mobile Dynamics polycrete" we came up with when we built the S'Cool Bus and Fusion Jetta years ago was a short name for "polyester concrete." My instructors came up with the idea to improve on the time required to work on the difficult materials currently available. For instance, polyester resin is hard but brittle, and auto body filler is too soft, but easy to sand. Through a bit of experimentation, they found that they liked the resulting blend much better. It was easy to work with and sanded well, but was extremely strong. The name polyester concrete was shortened to polycrete and we all just became used to calling it by that name.
Lately, Internet forums have been speculating and arguing about what polycrete is, and how we are being jerks for keeping it a secret. Even more sadly were the "guesstimators," offering their opinions on how we made polycrete - yet they weren't even close. Our Phase X class has been conducted over the weekend at least every other month for years, so there are a lot of graduates who know how to make and use polycrete. Apparently they aren't talking, yet it really isn't a secret.
It's a very simple formula - mix regular auto body filler with an equal amount of polyester laminating resin. That's it. In fact, it's so simple that others have stumbled onto the same idea independent of us. Comedian Mitch Hedberg used to describe a brand of soda as being made of just lemons and limes, but he tried it and it wasn't the same. How many people have tried to figure out the 11 secret herbs and spices that make Kentucky Fried Chicken and just can't get it right? I suspect that even if you had the famous formula for Coke in your hands, you couldn't knock it off.
The trick with polycrete isn't the mixture, but with the techniques used to make the product do what you want. I can't begin to describe how far to press your fingernail into the material as it is setting to determine if it's ready for the next step in the process. I can't tell you what color to watch for that indicates when it's time to begin sanding and shaping. It's a bit like trying to tell you how to cut hair over the phone.
Mix up a batch for yourself if you feel experimental. If you find you have a material you don't know how to use to its full effect, get in touch with Phase X.