What can I do to avoid sagging when I apply the color top coat?
In general, the recommended application for the bedliner (both base coat and top coat) is to apply at temperatures above 70 degrees. This will help promote rapid cure and avoid much of the sagging which otherwise might occur. The base coat is more easily applied to the verticals since you control the consistency with the powder additive. The top coat can be a bit challenging since it starts out thinner.
For the top coat, we recommend little (if any) lacquer thinner be added, and it is generally best to add in thinner coats. Depending on your temperature, the coats should “kick” (have an initial cure and be less likely to sag) after 15-30 minutes. You don’t need to wait until full cure to apply an additional thin coat since the product cures rather than drying (which would cause “skinning” of the surface and slow overall drying).
If you would like to add some of the lp80 to thicken, it would not cause a problem except that the color would end up being darker. The lp40 might appear speckled on close examination and would probably not be advised. We do have a product called amorphous silica (or fumed silica) which can be added to thicken without significant color change. The notation on using that additive is simply that it may create a very slightly cloudy appearance, but would not darken the finished product and would not likely be a problem for most bedliner applications.
If you need additional support, or would like to try the silica additive, please get in touch by email or phone so we can assist.