What is a heat mat? Its two sheets of plastic with an electroconductive ink squashed between it, this ink joins up to wires which you plug into the mains electric. When you plug the mat into the socket and switch on electricity flows down the wires and through the ink, the ink causes the flow of electric to slow down (causes resistance) which makes the heat mat warm up.
In the highest quality heat mats the ink is printed onto a glass cloth and is referred to as carbon impregnated glass cloth, this then has two metal strips sewn onto the ends and joined to the wires before being sandwiched (laminated) in between sheets of adhesive.
The other style of heat mat has the ink printed straight onto a sheet of plastic, usually in strips (known as tracks), sometimes in very fine strips. this method of production is cheaper than the glass cloth method and has certain drawbacks as i will now explain.
These heat mats are made by printing ink onto a sheet of plastic, so basically you have a silk screen printing machine just like the sort that is used to do t-shirt screen printing, onto that an electronically conductive carbon ink is poured and then an operator stands there putting in sheets of plastic which the machine prints with the ink,
Now because carbon ink is expensive the boffins who design these try to get the maximum coverage of area with the least ink possible, thats why the printed heat mats have tracks (black lines) on them that run from one end to the other.
During the printing process ink builds up around the stencil and its the job of a skilled printer to monitor the print quality and wipe clean the stencil and remix the ink whenever neccessary, if this doesnt get done then tiny hair line bleeds get printed which connect the tracks up in places where they shouldnt do which changes the resisitance of the circuit. Also if the ink isnt changed at the right time it starts to go off causing an uneven print surface which also effects resistance.
Once they are printed and dried its some poor sods job to sit in front of a light box with a high powered loupe or looking glass and they have to look at all the tracks on the circuit to make sure there are no defects, it would typically be something like 1 in 100 circuits that get inspected, so plenty of room for faulty ones to get through. at some places every product is given a final test before being sent off but i can imagine this isnt the case for all factories, if these ink bleeds are missed it could malfunction causing it to melt or catch fire.
Because the cloth mats are basically a solid sheet of carbon you dont ever get this problem!
So how do you know which is which, well its quite simple, glass cloth heatmats are only made by one company and thats Eurorep, they sell them under the brand name Habistat and manuafacture them for Komodo and also Pro rep, anything else and it will be a printed plastic mat, some manufacturers are now laminating there mats in black plastic so you cant see the thin tracks inside but unless its one of those brands it will definately be a mat of lesser quality. Another give away is if its made in china as all of the Eurorep mats are made in the UK.
We currently sell both types of mats on our website, the Habistat ones I would advise every time, and we also stock printed ones made by Lucky reptile, as of yet we have had zero returns involving serious defects with these mats on both brands. So i am guessing luck reptile have better quality control procedures than the unnamed but unavailable from us brand of heat mats!