HIGH-PRESSURE VS LOW-PRESSURE EQUIPMENT
High Pressure EQUIPMENT:
High-pressure guns don’t have static mixing tubes. Rather, the chemicals are mixed together right at the tip of the gun. The product is so hot and under so much pressure, that it sets — meaning it goes from a liquid to a solid — very quickly, in about three to five seconds. Because the 1:1 ratio of chemicals in the high-pressure yield a product that’s very rigid, you’re limited on the texture — which resembles the surface of 80-grit sandpaper.
LOW Pressure EQUIPMENT:
With low-pressure guns, the substance flows before it sets, leaving a flat glossy surface. Then, if your client desires, you can add a specific texture. Depending on which low-pressure gun you choose, liner texture can vary between raindrops and cottage cheese. However, the textures are more easily created with the guns that have the trigger switch, since you must periodically turn the system on and off to create the effect. Also, the guns without the trigger switch require you to check the chemical ratio each time you turn the gun on and off. The ratio is very important in all polyurethanes. If you’re not within a couple of percentage points of being right on the money, you’ll end up with goo.