Because of my background in plastics manufacturing I get a lot of calls and requests on how to care for your C4 Corvette Acrylic Targa Top. Basic maintenance of the roof goes a long way in increasing the life and look of the acrylic panel.
For a little background, when Chevrolet re-designed the Corvette for introduction in 1984, they designed a lot of great ideas used in other sports cars in the past. Instead of the T-Top roof panels that had been used in the Corvette C3 from 1968-1983, they opted instead for a Targa roof like the Porsche 911. The standard roof was a fiberglass panel painted the same color as the car. Chevrolet also had an optional moon roof which featured a bronze or blue smoked plastic. Originally Lexan was used in the roof in 1984, but was found to be easily scratched. Lexan is a very break resistant material, but the drawback for it’s break resistance is it’s soft surface which scratches fairly easily. As a side note all race cars use Lexan for their front windshields from the local tracks to the Nascar Nextel Cup Series. In the Nextel Cup and Nationwide Series the race teams use tear off films on top of the Lexan that can be removed during the race which minimizes the scratches to the windshield. Later in the 1984 model year, General Motors switched over to Acrylic with a scratch resistant coating to help prevent scratches in the roof.
Caring for a acrylic roof panel is easy. Wash the panel with mild detergent, standard car wash detergent from Walmart is fine. The key is to spray the roof with a hose well to remove any of the loose dirt BEFORE WIPING THE SOAPY RAG ON IT. After the roof is dry apply wax to the roof. It is important NOT to use a cleaner wax, repeat do NOT use a cleaner wax as it has abrasives to clean dirt and oxidation ground into the paint on a car and it WILL scratch the plexiglass roof. I suggest applying multiple coats of wax, and applying them often as the wax will burn off in the hot sun.
Removing deep scratches from the roof is a little more tricky, but if you are careful and cautious it should not be a problem. First you must sand the scratch out with 1200 grit sandpaper. Personally I use wet/dry paper and wet sand the scratch with water that has some dish washing detergent mixed in. The water acts as a lubricant to help keep surface scratches from the sandpaper to a minimum. After this step, dry the area and buff it out. If it is a small scratch, you can hand rub it out. Starting with heavy cut buffing compound buff out the area with a soft rag. Then buff it out with a finish cut buffing compound until all the scratches are out and the shine has come out. The last step is to apply a few coats of paste wax to the roof. If the scratch is large, you will need to use a buffing wheel. Before using a buffing wheel be sure you are experienced with it. If not, I suggest calling a car detailer in your area.
For fine surface scratches you do not need to use sandpaper, just hand buff the roof lightly with a scratch remover compound, like Maguire’s. It may take some time so be patience.