Based on the scientific principle that iron powder is oxidized to generate heat, when it is used, it is only necessary to open the anti-oxygen packaging bag and let it contact with air, so that oxidation reaction can occur and heat can be generated. The reaction principle of warm paste is to use primary battery to accelerate oxidation reaction and convert chemical energy into heat energy. In order to keep the temperature longer, vermiculite, a mineral material, is used to keep warm. Because it can't react before use, the material of the bag should be very special, consisting of raw material layer, gelatin layer and non-woven bag.

Under the action of oxygen in the air, the raw material layer in the warm winter sticker can continuously release heat within 12- 15 hours, and this reaction process begins when the vacuum packaging is opened.

Principle of galvanic cell: Hot paste is mainly composed of carbon powder, iron powder, water, salt solution and polymer to discharge, and then because there is no positive and negative electrodes, electrons cannot be separated from positive and negative electrons, directly forming a short circuit, thus generating heat.

The stability and durability of heat generated by hot paste are the key points to judge the quality. General13x10cm patches can be heated continuously for 12 hours (above 40℃) to be qualified, and those that can be heated continuously for 14 hours or more are the best products on the market at present.