Over the years in this profession, discussion and situations have been encountered with regard to which is the best glazing component for the best job. Normally, the options are between safety glass or plastics. There are different types of each.
Normal annealed glass is not recommended in marine use. Its not because we make more money from safety glass, its just that annealed glass breaks very easily. On the water, you are more inclined to trip, fall or stumble and stick your hand out to stop your fall. Imagine for a moment falling onto annealed glass that is wet, slippery and you hit it with force enough to break it, and add to the situation that you're 10 miles off shore!! This is why we don't recommend annealed glass. Besides that, it is not suitable for surveyed boats and should anyone ever want to put your vessel into survey, it would cost an arm and a leg to change it all.
There are two types of safety glass, Laminates and Toughened or tempered glass. Both have pro's and con's.
Laminated glass has an advantage in that when it breaks, it stays where it is and doesn't leave you with a big hole in your boat. Unfortunately, it breaks very easily and you must be prepared to replace it. It also has a tendancy to de-laminate around the edges. I'm sure most of us have seen it in marine situations where it looks like there is a growth between the two sheets. It looks unsightly and has to be replaced. As laminated glass is simply two piece's of annealed glass stuck together with a clear interlayer, it qualifies as safety glass but is difficult to live with.
Toughened or tempered glass is very strong, rarely breaks and is permanent from the point of view that it is one solid piece of glass. It's only down side is that should you hit it hard enough to break it, it shatters into millions of small pieces of glass, rendering it non threatening, but leaving a hole in your boat! Toughened Tempered glass is many times stronger than Annealed and is safe to work with. It is our opinion only that this product is the best option, and if you are worried about breakages, throw a piece of polycarb in your engine room somewhere big enough to place over a broken pane, in the event that you ever break one. It is a rare occasion.
There are two types of plastics, Acrylics and Polycarbonates. Acrylics are the harder of the two and more resistant to scratching. Surface scratching and deterioration is a common complaint with both types of plastics. Gentle cleaning is the key and try to limit this cleaning and polishing as there is normally a film of UV filter on the surface and the more you clean / polish it, the thinner this gets, letting more and more UV in to attack the plastic. Once cracking or crazing has occurred, it can be polished out to some degree of success, but the UV film is then completely gone leaving the plastic fully exposed to the sun, and all its harmful rays. Plastics are normally used where there is curve or whined in the boat, and glass cannot be fitted. It is also used where impact is likely for instance around anchor retrieveal area's. Polycarb is shatter proof, where as Acrylics will crack but rarely fall or leave shards with jagged edges. It is also very light compared with glass