I would probably test it for longer, maybe stand on it for 24hrs, before placing your mirror on it. Better safe than sorry.

Wrong. Studies have shown 27 hours in the minimum.

I’ll stand on it. If it can survive me it can handle any mirror! Lol

Are you sure its 130 pounds? 1/4” glass weighs 3.25lb/sq ft. Your mirror is most likey 3/16” thick at best, so 3.25 pounds X .75 = 2.4375lb/sq ft which means you have a 53 sq ft mirror?

In any case, with a mirror that size, I would make sure it has safety backing on it. Bascially its a glorified sheet of sticky stuff on the back that keeps it in 1 piece if it were to fall, or something hit it.

Dammit, I wish I'd known that before installing my mantelpiece.

It seems I overestimated, it's actually 112 lbs. I have the 5 foot mirror:

https://www.anthropologie.com/shop/gleaming-primrose-mirror2?category=mirrors&color=020&type=STANDARD&quantity=1&size=5%27

You could also have 27 people stand on it for one hour if you are an efficiency freak

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According the website, the mirror is meant to be leaning against the wall with the base at least 3.5 inches from the wall. Do you have room on the mantel to set the bottom of the mirror that far from the wall? If so, the part of the mantel that needs to hold 112.5 pounds needs to be the part 3.5 inches from the wall. The cantilevered part of the mantel will hold less weight that the part right up against the wall.

What kind of supports does this mantel have? Is it supported with legs on either side? Or is it cantilevered across the whole span?

I think Factors of Safety for civil engineering are like 3 to 4 ... not that you should take my word for it.

The honest answer is no, that test would be insufficient to verify the weight capacity. Under ideal conditions an aluminum can can support your weight for five minutes.

A properly anchored mantel, though, can support 50lbs per stud (18"). So if your mantel was installed right and is of standard width, it should be able to hold 150+lbs.

If I'm reading it correctly the 1997 MRI standard for commercial shelving says to test to 1.5 times the design load, measure the deflection, leave it under load for 15 minutes, and measure the deflection again. If it increases by more than 5% in 15 minutes, or stays deflected more than 15% of the final deflection after the load is removed, it fails the test.

http://scholarsmine.mst.edu/cgi/viewcontent.cgi?article=1000&context=ccfss-rmi

There's a newer standard but it doesn't seem to be available online.

If your mirror weighs 112 pounds you would want to test to 112*1.4=168.

Personally I would test with milk jugs or something (figure a gallon jug of water is 8 pounds, a 5-gallon bucket is 40 pounds) rather than standing on it--if it breaks, water on the floor is a lot easier to deal with than broken legs.