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While we have done some etching of glass with hydrofluoric acid alone, to achieve a matte white finish on float glass, I am curious to know what formula and procedure is required to create a more transparent and smooth finish ?

(Lead crystal polishing is achieved after diamond grinding, dipping in a mixture of $\ce{HF}$ and $\ce{H2SO4}$, and alternating with rinsing.)

Can anyone advise on the possible advantages of mixing another acid with the $\ce{HF}$?

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    $\begingroup$ I find the "matte white finish" and "a more transparent and smooth finish" contradicting. If it's the latter you are after, why etch glass at all? The purpose of etching is to reduce transparency and smoothness, not to increase it. Or are you using etching for shaping/printing on the glass surface (e.g. something like a PCB)? $\endgroup$ – andselisk May 28 at 11:02
  • $\begingroup$ what about using potassium hydrogenfkuoride KHF2 instead of HF?en.wikipedia.org/wiki/Potassium_bifluoride "Potassium bifluoride is the inorganic compound with the formula KHF2. This colourless salt consists of the potassium cation and the bifluoride (HF2−) anion. The salt is used in etchant for glass. Sodium bifluoride is related and is also of commercial use as an etchant as well as in cleaning products." $\endgroup$ – Poutnik May 28 at 21:39
  • $\begingroup$ I appreciate the responses. The desired result is for the surface to be etched either with acid or sandblasting while leaving raised dots by masking with a resist. The etched surface is required to be semi transparent and not matte white. We are considering either doing the etching by sandblasting then 'acid' etching the sandblasted surface to render it more smooth, or doing all the etching with a liquid etchant which will also achieve the required finish. $\endgroup$ – Michael Guy May 30 at 17:16
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Alkaline etching of glass tends to be less rapid than HF and leaves a smoother surface. This may not be what you do for the first etch on fresh glass, but it may smooth out the etch somewhat after an HF etch. The smoothing may also be caused by silicate ions that form in the alkaline etch fluid, so perhaps a solution of potassium (or sodium) silicate (ortho or meta) would be gentler. A polysilicate might be too slow.

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