Potassium nitrate

Glass Chemical strengthening with potassium nitrate salt: consist on an Ion Exchange between sodium and potassium. Sodium comes from the glass and potassium from the Potassium Nitrate. When potassium replaces sodium, because the atom is bigger, it firstly causes glass expansion, but later on it causes a Surface compression that allows the glass to get stregther.

Surface compression test is performed by the Quality Control lab of glass manufacturers to evaluate the effectivity of the Ion Exchange and the quality of Potassium Nitrate.

There are 3 type of glass:

• Soda Lime Silicate glass (SLS)
• Sodium Alumino Silicate glass (SAS)
• Lithium Alumino Silicate glass (LAS)

SLS and SAS glass are processed by Potassium Nitrate. During Ion Exchange, sodium in the glass is replaced by the Potassium of the salts. LAS is normally processed by Ion Exchange in a Sodium Nitrate bath.

Quality Chemicals offers the following products suitable for glass chemical strengthening:

• Potassium nitrate, our code 145804, PS grade
• Potassium nitrate, our code 145827, PAI grade

PAI grade has a lower sodium content than PS:

• PS →  Max 0.1%
• PAI → Max.0.01%

If mineral sources of Potassium nitrate are used, with higher sodium content, Customer will need to use additives from first day. Apart from this, some mineral sources have a lot of calcium that may also interfere in the Exchange. It is highly recommended to use synthetic potassium nitrate origin from Quality Chemicals.