The revolutionary TherMark process uses precise lasers and marking materials scientifically formulated to permanently fuse to metals, ceramics, glass and other hard surfaces creating high-contrast, high-resolution marks. TherMark’s patented technology offers an unmatched combination of benefits that stems directly from the chemistry involved in its laser marking process.
TherMark’s marking materials, or inks, consist of traditional ceramic glazing material, with the addition of a thermal absorber. The ceramic glazing material is a mixture of glass frit – small particles of partially fused glass designed to melt at a much lower temperature than ordinary window glass – with pigments for coloring. The traditional use of such glazing material requires it to be applied to the surface of a ceramic object, and then baked in a very hot kiln for more than an hour. Once fired, the glass frit and pigments combine to form a thin layer of colored glass that is further fused onto the surface of the ceramic object.
The patented TherMark method uses a laser as the heat source to fuse the ceramic glaze instead of a kiln. All this happens in microseconds as opposed to hours, consuming far less “energy” and, consequently, without compromising or damaging the material being marked. It is the thermal absorber within the TherMark marking materials which enhances and speeds the heat absorption from the laser beam, improving the transfer to the glaze. The thermal absorber is also instrumental in allowing the substrate to be marked using multiple laser types. For example, a CO2 laser cannot mark most metal because the beam cannot be absorbed by the substrate. Because of the absorbers, TherMark facilitates marking metals with a CO2 laser, increasing the range of applications the laser system is capable of.
The inclusion of pigments in the TherMark marking materials not only enables the creation of high-contrast, high-resolution marks, but also provides the ability of tailoring the color to the application. The pigments used are chemically similar, in many cases identical, to the ones used to decorate fine china, ceramics and tile. Some of these pigments undergo no chemical change during the laser firing process and either dissolve into or are simply encapsulated by the melting glass frit. Others react with the molten glass frit and with each other to “develop” the desired color under the laser’s heat. For example, TherMark uses a proprietary cobalt compound as a pigment which develops a deep blue color by reacting with the silicates in the glass frit to form Co-silicate.
In all cases, the result is a high-contrast, colored mark composed of inherently stable pigments which are further protected in capsules of inert glass.
The use of chemically stable pigments is one of two keys to the formation of permanent marks within the TherMark process. Equally important is the thermal bonding process. As the glass frit melts, it chemically bonds to the substrate’s surface. In the case of a glazed ceramic or glass substrate, silica atoms in the frit bond to the silica atoms in the ceramic glaze or the glass surface through an oxygen atom, as shown in Ilustration 2A below. In the case of unglazed ceramic or metal, silica atoms in the frit bond to metal atoms in the ceramic or metal surface, again through an oxygen atom as shown in Illustration 2B. These chemical bonds are as strong as the bonds holding the glass together and result in a mark that can stand up to severe abrasion and corrosion.
The components of the TherMark marking materials vary in order to address a wide variety of target substrates. Additionally, these marking materials are further mixed with either a liquid carrier – water or ethanol – for the ink and aerosols or otherwise bound to transfer tape.