Question

The MSDS for various glass etching creams all show that they're primarily composed of 4 substances (the composition percentages vary):

Ammonium Bifluoride - 20 - 40%
Sodium Bifluoride - 5 - 10%
Sulphuric Acid - 1 - 5%
Barium Sulfate - 1 - 5%
The purpose of the fluoride ingredients is obvious. They decompose into hydrofluoric acid (presumably when reacting with water in the air) and do the actual etching. But why is there Sulphuric Acid? It doesn't react with glass at all.

My speculation would be that perhaps it's a strong desiccant and it serves to slow the reaction?

Answer 1

Sulfuric acid in glass etching creams serves as a catalyst, removes impurities on the glass surface, and creates a stable solution for easier application and control.

Step-by-step explanation:

The presence of sulfuric acid in glass etching creams serves several purposes. Firstly, sulfuric acid acts as a catalyst, speeding up the reaction between the fluoride ingredients and the glass, thereby enhancing the etching process.

Secondly, it helps to remove any impurities or oxidation on the surface of the glass, allowing for a more even etching. Finally, sulfuric acid also helps to create a stable and viscous solution, making it easier to apply and control the etching cream.