The Lost Art of Burglar Alarm Window Foiling

Ride thru an area with an older business district full of main street shoppes and you may come across a shop with windows which have silver or gold trim around them While some places do fancy designs on glass windows these silver and gold stripes where for protection from burglars. The tape was made from lead and other materials and wear wired into a burglar alarms circuit. When installed on tempered commercial glass windows such as you see at left if an intruder attempted to break the glass or cut a circle in it the tempered glass would shatter and split breaking the metal tape and breaking the alarm protective circuit setting off the alarm system.
While this was the common way to protect windows when I started in the industry by 1980's it started falling out of favor for sensors placed on glass or audio detectors which heard sound or vibration detectors which felt break in attempts. The last set of windows I foiled are at left I did in late 80's for a shop owner who wanted the old fashioned look with diamond corners for his recently remodeled store front made to look like it was from 1930's .
While it was fun to make the designs it was not easy t do so. Foil was applied by first putting down a layer of clear adhesive with a brush then when it got tacky you applied tape then put a layer of lacquer over it. If it was a warm summer night no problem when windows where cold forget it . They also towards the end of foiling days had self adhering foil so you did not have to put on a first layer of adhesive but it worked no better if cold either.
To do the multiple panes of glass plus door took me 2 days to complete and while this foil has been carefully preserved by the owner it was a pain in the butt because of lazy window washers breaking it or shop owner or his employee placing tape over and breaking it when they would remove a sales sign or customers would deliberately damage it on doors or burglars would do it acting like a customer casing a joint because it would disable alarm and some shop owners would not wait for repairman to arrive and leave . Which gave time for burglars to break in later in the evening. While foil could not be beat it was labor and maintenance intensive.
Which is why it has all but disappeared. I still have a couple customers who have it and when those windows get broken or otherwise replaced the foil will not be replaced. It very hard to even find the supply's for it any more.
To meet UL burglar alarm requirements it had to be placed at least 3 inches from frame and had to be on at least 3 sides of the glass. If the glass was wired mesh glass like you use to find in gym doors etc. or not tempered the tape had to be run back and forth every 3 inches. Which many owners objected to but if you did not do this a circle could be cut in glass and jumper put across contacts in an attempt to defeat the foil. Today its rare to see glass it self being protected by a sensor on glass usually its only high ticket jewelery stores that still do it or merchants that have high value items in there windows .
Since audio detectors and shock /vibration detectors have become so much better at detecting break in's and have become less false alarm resistant on glass protection is slowly fading away as well.

I should also be noted that foil was also used to protect walls from being broken thru as well before motion detectors where perfected and was placed every 3 inches . It was a wider foil which was put on thin plywood or similar wood then a thin cover of wood was placed over it to protect it and an intruder trying to cut thru a wall behind a safe etc would trip the alarm .