I think I have seen somebody do something similar on here before, but here is my take on it with a few lessons learned.
I was tired of estimating how much water was in my carboy and wanted a permanent solution. My wife has a Cricut machine so I employed her to cut out some markings in sticky vinyl to use as a stencil. Seen below.
This step took me awhile to decide what to use for my "official" measure. I ended up measuring out 2 cups of water by weight with a powder scale (this took awhile) and found my Oxo 2 cup measure to be nearly dead on. So then 2 cups at a time I measured each mark out.
I used a combination square to make a reference line with a dry erase marker. Another way to speed this up is I found it easiest to have a larger vessel to pour each 1/4 gal. into. After I added it I would measure out the next pour while the water settled down in the carboy. This served a double purpose to every time I added water I knew I needed to make a line I got ahead of myself once and added a line at the 1/8 gal. and it took me a minute to be sure of what I had done.
After I got all the marks added I used Armor Etch (shown below) to etch the glass. The instructions said to apply it for 60 seconds it took me several minutes to get it added to all the lines and I still wasn't happy with how solid the etchings were. Luckily I planned for this and washed it off lightly and I was able to apply a second coat and left it on for a good 10 mins. I think it turned out pretty well.
I was tired of estimating how much water was in my carboy and wanted a permanent solution. My wife has a Cricut machine so I employed her to cut out some markings in sticky vinyl to use as a stencil. Seen below.
This step took me awhile to decide what to use for my "official" measure. I ended up measuring out 2 cups of water by weight with a powder scale (this took awhile) and found my Oxo 2 cup measure to be nearly dead on. So then 2 cups at a time I measured each mark out.
I used a combination square to make a reference line with a dry erase marker. Another way to speed this up is I found it easiest to have a larger vessel to pour each 1/4 gal. into. After I added it I would measure out the next pour while the water settled down in the carboy. This served a double purpose to every time I added water I knew I needed to make a line I got ahead of myself once and added a line at the 1/8 gal. and it took me a minute to be sure of what I had done.
After I got all the marks added I used Armor Etch (shown below) to etch the glass. The instructions said to apply it for 60 seconds it took me several minutes to get it added to all the lines and I still wasn't happy with how solid the etchings were. Luckily I planned for this and washed it off lightly and I was able to apply a second coat and left it on for a good 10 mins. I think it turned out pretty well.