I don't know where your making this stuff up from but, when I test my magnets with my magnetometer I measure the strength of the field produced in Teslas. I never learned anything about these "spots"
Must be that new, "I don't know WTF I am talking about but, can make it sound like I do school of physics" you attended.
In all of the years that I have worked in this industry and with more companies than I can count, not a week goes by that I do not receive an inquiry about problems associated with magnetic signs or magnetic material.
I have wrote more magnetic care instructions, company product guarantees, and reports for sign companies in which we have tested failed materials and outlined our findings so that they can submit claims to the manufacturer if/when applicable.
I have a wide variety of specialized testing equipment at my disposal, such as instruments to measure the tensile strength of banner material and other similar materials to ensure that the material a client may have purchased is in fact what they received (this is a common issue when some companies buy in large volume direct from a manufacturer) for example a client specifies that they need '13 ounce vinyl banner material - three-ply w/ PVC outside layer -800 denier polyester scrim' and when tested it jreceived and tested it specs out at 11.875oz and 500 denier...it isn't the end of the world if you have just received a single roll of material that doesnt meet your expectations, but if you have received a shipping container from China with a few hundred rolls of material that doesn't meet specifications/expectations it is a serious and costly situation.
But in regards to magnetic material, again I have tested literally every brand that I know of for many clients, I have been in hundreds upon hundreds of sign shops and I have NEVER encountered a sign shop that owns a magnetometer.
I can just picture a sign shop in the course of their day while producing signs breaking out their magnetometer to measure the strength of the magnetic field of the magnetic material they are using, lol. I would LOVE to hear from a sign shop that does this as a part of their standard operating procedure in manufacturing magnetic signs...and Addie, sorry you don't count because you don't make anything.
Not that a magnetometer is an expensive piece of testing equipment, it is just that the whole concept brought up here by someone who doesn't manufacture signs is just down right comical and shows the complete and total lack of understanding of the day to day operations of a real sign shop. Even more comical in my mind as he attempts to attack a newer member who obviously does make signs with such a bizarre concept...
Ok I'm going to go and setup my magnetometer and test these magnetic signs before i send them out and then I'm going to set up my Elmendorf Tear Strength Tester to test the ballistic tear strength of this birthday banner that needs to get finished, I'd hate for this man to swing from it and find out that it was only rated for 385 pounds when it looks like he's been spending a little extra time at the buffet
....lol...who am I kidding, I haven't made a sign for years.
we need a 'rolling eyes' smiley