Glazing weight Tip

JohnR

MGF, Master Grumble Framer
Joined
Jan 1, 2005
Posts
542
Loc
Ohio
This may be of some use. In large pieces (over 40” rabbet on longest side – or so) or mirrors and plexi box pieces, the glazing/glass weight can become an issue.

Use the following formula to calculate the weight of the glazing:
Height X Width X Thickness X Density = Weight
The density of glass is .09 pounds per square inch. Plexi is .043

Typical thickness of float glass in decimal inches:
.080 picture
.090 single strength
.120 double strength
.190 “3/16” glass
.230 “1/4” glass

Example: weight of mirror with 1/4” 60 X 48” glass
60 X 48 X .230 X .09 = 59.6 pounds
Add the weight of the framing and that = one heavy mirror!
HTH, John
 
Interesting John,
For framers living with metric, it's even simpler (well, to us metric folk anyway).
Eg. . .
2mm picture framing glass = 5kg/m2
3mm glass = 7.5kg/m2
6mm glass (mirror) = 15kg/m2
So, you just take the m2, say 1220mm x 610mm (48" x 24") is 1.22 x 0.61 = 0.744,
for say 6mm (1/4") silver mirror x 15kg = 11.16kg of glass.
I'm sure plexi suppliers could provide the m2 weight of different thicknesses if asked.
 
All the glass I use is essentially the same thickness (within tolerances, anyway) so, a while back, I weighed a 10" square piece on my postal scale to get a weight per sq inch and added a formula to my POS to give me the glass weight for a particular frame size.

I did that so I could respond with authority to customers who insisted on a 75# hanger for their 16x20 frame. (That glass weighs about 2-1/2 pounds.)
 
Interesting JohnR

I aint no math wizard but 12.96lbs per square foot of glass sounds just a little high.

I'm big and strong, but I for some reason that 32" x 40" sheet doesn't seem to weigh 115lbs.

square inches in a foot 144
times the lbs of glass .09
equals 12.96lbs

32x40 is 8.88 sq" = 115.01lbs

what did you get Ron?
 
Pat,

About 1.16 lb/sq ft or about .008 lb/sq inch.

This is pretty close to John's numbers for single strength glass.

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Baer, ya gotta multiply your number by the thickness of the glass.

32 times 40 times .09(density) times .09(thickness for single strength) = 10.37 pounds.

I moved a lot of 32x40 glass recently and I would have noticed if a lite weighed 115 pounds.

With my formula, I get 10.28 pounds. The great thing about John's numbers is it allows for thinner picture glass or thicker mirror glass.

I always guessed that acrylic is roughly half the weight of single strength and it looks like I was close-enough.
 
Yup. About 10 pounds sounds like what if feels like.

Like I said Ron, this kid ain't no math wiz.
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Now if I could just figure out how to wipe out my previous math figures.......

oh, what an embarassment...
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