Why does glass etching cream contain sulfuric acid?

The [MSDS](https://www.glassetchingsecrets.com/wp-content/uploads/Armour-etch-SDS-2015.pdf) 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?


