The Issue of Ceramic Plate Weight
Nothing written below should be relied upon to build or consider to build your own armor and it is not considered advisable to do so.
I get this question a lot -
"How heavy are your Alumina ceramic armor plates?" Ah, what a loaded question!
Let's just use a single plate model as an example: an NIJ 3+ plate.
A common method of manufacturing ceramic plates is to leave about 1" (25mm) of space between the edge of the ceramic and the edge of the UHMWPE (Ultra High Molecular Weight Polyethylene) back plate. This 1" around the edge of the plate makes the armor plate lighter, it protects the ceramic edge somewhat and allows significant deviations between manufactured ceramic sets and the normal tolerances of back plates coming out of the mould. This 1" foam edging around the ceramic perimeter results in an actual NIJ 3+ protective area of just 8"x10". For some people very concerned about overall weight, this is acceptable. This style of manufacturing for a 3+ plate generally results in a total plate weight of about 5 pounds. Other plates (including Level IV) are manufactured in this way also but use thicker back plates and ceramic tiles (10-12mm is common).
The actual weight will of course be relative to the back plate thickness and the ceramic thickness chosen. Some manufacturers use a 7-8mm back plate and an 8mm alumina tile. Others use a 10mm back plate and an 8mm or 10mm tile for 3+ coverage. Knowing these details (ask your manufacturer) will allow you to understand more about the ballistic resistance of your armor. The important part of this story is that with a defined back plate thickness and ceramic mosaic tile thickness - the "weight" will change according to overall ceramic coverage.
There is another way of manufacturing which leaves about 12.7mm of space along the edge of the plate where no ceramic exists. This extra 1/2" of ceramic (relative to the first paragraph) increases the ceramic coverage area by an additional 1" horizontally and 1" vertically. This means that your 10"x12" plate will have a ceramic coverage area of 9"X11". But, this extra coverage comes at a price - the weight of the plate increases by approximately 1 pound. So, the Level 3+ plate we started with in the first paragraph is now a 6 pound plate. When I am asked about "weight," the customer seems to automatically think that lighter is better. They have a right to want a lightweight plate - but there seems to be a misunderstanding and lack of awareness that the weight is increasing because the ceramic coverage is increasing.
"Edge to edge" coverage is when the ceramic completely covers the back plate (or nearly so). There are times when ceramic and/or back plate manufacturing processes result in deviations within .5-1mm tolerances and that can create slight misalignment issues. These minor problems are normally covered up with edging. Adding edge to edge ceramic coverage is the heaviest configuration yet... and a plate with the NIJ 3+ label we talked about above is now up to 7 pounds.
The point of this discussion is that weight is not always a bad thing. For a given manufacturer's configuration, the weight will increase as ceramic coverage expands.
WG
