I've never been asked that question, but in response to "is the bag strong?" I say, "the material can not be ripped by any man I know, (meaning the phone book rippers may be able to rip the bag, but I don't know any of them) and because of the strength and composition of the fibers, it will not rip - even after being cut. You can see a stress test of the fabric holding a forty pound container of water here.
In preparation for retail sales of The Brew Bag, we did all manner of testing on the material and the strapping. We pulled a car, cut a hole in it and tried to rip it with our hands in the hole, put three bowling balls in the bag and yanked it with the winch, we even tried a two man pull. The material can not be ripped and does not "burst" under any normal brewing circumstances.
Our replacement / return policy is very simple. If the bag is defective in any way from a manufacturing perspective we'll replace it at no cost. After two years in business, that's never happened. We're not saying it can't happen but so far our ratio of success to failure is 100%.
Here's what we don't do - we don't refund your purchase price when you cause the problem. I received an email from a customer stating that the bag "burst" when he lifted his first batch out of the kettle. He said it was ten pounds of grain and he thought that based on the web info, that shouldn't have happened. He was right, because it didn't happen that way. My reply to him is below.
...And we know a fair amount about fabric, stitching,weight
parameters and weight distribution.
The bag you purchased is constructed of Voile, a polyester material with a 90
thread per inch count. By itself with a simple lock stitch, it can hold over 100
lbs - without the strapping - with the strapping and the weight of grain
distributed across the fabric evenly as it comes out of the wort, it can hold in
excess of 150 lbs. The straps have an extended failure point of 300 lbs and an
initial burst point of 260 lbs. The thread is polyester and when stitched to the
polyester strapping, through the polyester bag at 10 stitches per inch creates a
seam strength of 39 + lbs - on the horizontal - when attached to the strapping
and unless stressed horizontally it will not break free and thus conveys the
strength of the strapping on the vertical. All brew bags are lifted vertically
out of the kettle. The photos of the bag you sent show the fabric ripped away
from the stitching through BOTH sides. The seam remains on the strapping with fabric
still attached under the strapping - AND the fabric is pulled away from a second
piece of strapping as well.
That is IMPOSSIBLE to replicate EXCEPT when the bag is caught on something sharp.
The ten lbs of grain you used absorbed 180 oz of water before squeezing. The
initial lift weight of the bag, plus grain and excess water was between 50 and
55 lbs - with an estimated drain off rate through the bag of 3 gallons per 30
seconds leaving. This total lift weight is actually never realized as the water
begins to drain as the bag is being lifted and before it clears the water level,
so the actual initial weight is not born by the bag or the straps, however, when
fully lifted out of the wort, the actual weight of your ten gallon batch was
between 12 lbs 8 oz and 14 lbs, which is well below the bursting HORIZONTAL
strength of ANY of the materials used, let alone the VERTICAL burst weight.
This is the photo of his bag - you can see that the seam of the bag is still attached to the strap. And since two grown men can't rip the fabric we use, we wondered what caused the bag to be ripped. In order to consider the story as a testimony of what it takes to tear a bag like this, we asked him to tell us the story about how the bag was actually ripped. He declined to comment.