BOROSILICATE Glass

[Jason1979]

Hello all

Anyone have any experience with grinding/sanding glass, well Borosilicate glass to be precise. I have four 2" sight glass for my build and noticed that the ferrule ends are not plumb (level) meaning my column may look a little wonky. I've taken them apart to clean with pbw and can see that the Borosilicate glass tube hasn't been cut a true 90 degrees, but have a very slight angle to them and as PTFE isn't very forgiving, it means the Stainless steel section bolts down on the wonk.

I have cut granite and marble before using a small angle grinder with a diamond disk, but never done any glass work. Could this be a DIY fix?

Thanks

[Tony1964]

Hi Jason

I had this with mine, notified the supplier (in China) and they sent out new sight glasses FOC, send them a picture of how far off they are.

Cheers

Tony

[Jason1979]

Hi mate

Yeah I think I will but for the sake of a months wait and if I had the tools for such quick modification, happy to do it myself. But yes, contact the supplier for sure.

[Bushman]

Unforntunately our resident expert passed away a couple years ago. If you have any glass blowers in your area I would suggest you contact them and they should be able to answer your question.

[amh71]

The best way would be to do it by hand, power tools are likely to make too much friction and end with a cracked tube unless done underwater.

I would take a sheet of greenhouse glass and add a few teaspoons of silicon carbide grit, about 200 grit, add enough water to make a slurry and then holding the tube as vertical as you can grind in a circular motion, don't apply too much pressure or go too fast, you don't want to introduce any heat. When your arms ache its probably done.

You may get away with a sheet or wet&dry paper, kept wet or a diamond hand pad but the carbide would be best.

I'd consider annealing the tube afterwards for safety if you have access to a kiln.

[Twisted Brick]

I would take a sheet of greenhouse glass and add a few teaspoons of silicon carbide grit, about 200 grit, add enough water to make a slurry and then holding the tube as vertical as you can grind in a circular motion, don't apply too much pressure or go too fast, you don't want to introduce any heat. When your arms ache its probably done.

I would tape a carpenters square to the glass to identify the protruding 'leading' edge. Then carefully start my hand grind with the offending edge to bring it square and avoid just grinding away glass.

[hefezelle]

Anyone have any experience with grinding/sanding glass, well Borosilicate glass to be precise.

I am a hobbyist glass blower and regularly cut and sand borosilicate glass. What you want is running water, sand paper that can stand being wet, a stand to rest the glass allowing for rotation (such that the sanded face will be planar and level), and ideally a machine that moves the sand paper AND can take being splashed with running water. If you don't have access to such an industrial machine, a lot of elbow grease will be required. The important part is that you have water cooling the glass while you sand it, that you don't apply much pressure when sanding, that the paper has a planar surface behind it, and that you slowly rotate the glass while sanding it.

Annealing will not be needed, unless you want to heat the sanded surface to give it a glossy, clear finish.

I like the idea of strapping a carpenters square to the glass, but it would be even better to have a rest for the glass piece in a horizontal position, while the sand paper runs vertically downward. That's the setup in the glass shop, anyway.

Good luck, keep us posted about how it goes!

[OtisT]

I went through the same issue with a non-level sight glass and was able to fix it without grinding.

After taking it apart, I found that not only was the glass off by 1/64” on one side, but one (not both) of the SS ends was also off by 1/64” on one side. I put the high ends of each bad part on opposite sides and Shazam!, it was perfect.

I also learned a few tricks to tightening sight glasses that I can share if you want that input. The first assembly leaked, but I came up with a method that worked well to seal things well. I actually took pics of my repair job, so I can show you if you are interested. It was a learning experience for me, but now I’m comfortable assembling these things.

Otis

[The Baker]

Not the same at all.
But I had some poorly made decanters, the glass stoppers were not a close, neat fit in the neck.
So I used automotive valve grinding paste to lap them in.
With mixed results, some did not have enough glass and the stopper sunk in too far. But basically it works.

Geoff

[Jason1979]

I went through the same issue with a non-level sight glass and was able to fix it without grinding.

After taking it apart, I found that not only was the glass off by 1/64” on one side, but one (not both) of the SS ends was also off by 1/64” on one side. I put the high ends of each bad part on opposite sides and Shazam!, it was perfect.

I also learned a few tricks to tightening sight glasses that I can share if you want that input. The first assembly leaked, but I came up with a method that worked well to seal things well. I actually took pics of my repair job, so I can show you if you are interested. It was a learning experience for me, but now I’m comfortable assembling these things.

Otis

Hi Otis

I was thinking that maybe the issue at first, but yes, please share as I would find it interesting for sure

[Jason1979]

Anyone have any experience with grinding/sanding glass, well Borosilicate glass to be precise.

I am a hobbyist glass blower and regularly cut and sand borosilicate glass. What you want is running water, sand paper that can stand being wet, a stand to rest the glass allowing for rotation (such that the sanded face will be planar and level), and ideally a machine that moves the sand paper AND can take being splashed with running water. If you don't have access to such an industrial machine, a lot of elbow grease will be required. The important part is that you have water cooling the glass while you sand it, that you don't apply much pressure when sanding, that the paper has a planar surface behind it, and that you slowly rotate the glass while sanding it.

Annealing will not be needed, unless you want to heat the sanded surface to give it a glossy, clear finish.

I like the idea of strapping a carpenters square to the glass, but it would be even better to have a rest for the glass piece in a horizontal position, while the sand paper runs vertically downward. That's the setup in the glass shop, anyway.

Good luck, keep us posted about how it goes!

Would a tile cutter work, I have one that has a water tray, not used it for years but I’m sure it has a diamond disk but unsure it will work like a disk sander (cutting on the side of the disk not the thin end?

[OtisT]

Hi Otis

I was thinking that maybe the issue at first, but yes, please share as I would find it interesting for sure

Sight Glass (SG) Assembly

I’m not a pro. This is just how I do it with my SG.

1. One stainless steel end of the SG should have all four threaded rods securely tightened. This involves tightening the first and second set of nuts on the bottom section. (First and second set, counting from the bottom.). You will not adjust this end of the SG again in this process.

2. Place the SG ferrule side down, rods up. I will refer to this as the Bottom of the SG.

3. Insert the silicone gasket into the bottom of the SG then place the glass tube into the gasket. Give a little twist of the glass to ensure is is seated evenly in the cup. [on my SG, the glass tube has a high side and one ferrule end has a high side. Both off by 1/64”. I have marked the high side of each item to easily see where the high spots are so that I can line them up on opposite sides]

4. Lower the third set of four nuts below their final adjustment location.

5. Insert the silicone gasket into the top ferrule section and gently lower the assembly into place on top of the glass tube. The top section should be resting on the glass tube and not the nuts, which were lowered previously. Give the assembly a gentle wiggle to ensure it is seated fully and that the top section is perfectly aligned over the bottom section.

6. Put very gentle pressure on the top of the assembly to hold it steady then gently raise the third set of nuts to the top ferrule section. Use feather light pressure only when raising nuts, and stop as soon as the nuts first touch and stick to the top assembly.

7. Without moving the nuts place a small piece of tape on one face of the nut and a second piece of tape just above the nut on the top ferrule assembly. Repeat for all four nuts.

8. Draw a vertical line on the tape for each pairing. These lines must be exactly vertically aligned and represent your base (starting) location for future adjustments.

244A7E92-A9EE-4884-812C-C50060BE8905.jpeg

9. Gently thread each of the fourth (top) set of nuts down onto the assembly and finger tighten only, ensuring the bottom not has not moved.

10. For each of the four sets of nuts, use two wrenches to tighten each set one at a time. The bottom nut should not be moved at all. Hold the bottom nut in place with one wrench while tightening the top nut. Tighten firmly from the top nut. The lines should be used to ensure each bottom nut has not moved.

11. Leave the tape on until after your SG passes the leak test.

12. Test for leaks.

13. My first assembly leaked because the overall assembly was a bit loose. I reversed step 10, loosening each top nut while holding the bottom nut in place. I lowered each of the bottom nuts just a fraction of a rotation. You can see how far I adjusted these down in the pic below. Repeat steps 9 and 10 to tighten the top nut. Retest.

B0837D5A-26DA-4F0A-AA56-3D4DBE03E1CB.jpeg

I stopped the leak in my SG after the first readjustment shown above.

Otis

[Kindafrench]

I had a leaking sight glass yesterday. This was the second run it had. No leaks in the first run.

Didn‘t want to use the original silicone gaskets, so I bought a sheet of 3 mm soft PTFE and cut two gaskets.
As far as I know, soft PTFE compresses a bit under pressure and then stays compressed, which possibly caused the leak.
I could not find out, where it was leaking as I checked the SG with a mirror, but I could smell ethanol / acetone. Must have been very small. I tightened the nuts a bit, but beeing afraid the glass would break under too much pressure, I let it leak and opened up all windows, to get a proper wind draft through the room.
During the run, I got confused by all the ethanol smell from cuts glasses and the fermenters in the room, meaning, I couldn‘t find out if it was still leaking or if it sealed itself by reexpanding or whatever.

At the end, I decided to change the sightglass location from under the reflux return to the condenser, which is the highest part of my still and has the least pressure.
I will disasseble the SG before moving it to it‘s new home and have a closer look at the gaskets.

To answer the sanding question, here is what I did:
I took my stop angle and used it on the glass. There were two spots, which were slightly out of angle, a bit wobbly. About a millimeter maximum. Having a stationary disksander in my shop, I was lucky to be able to fix it easily.
I leveled the sander, as good as I could, using the same stop angle. Glass doesn‘t like heat on a small spot, so I avoided putting pressure on the glass and let it gently slide against the 120 grit sand paper disc, while continuously turning the glas counterclockwise. The glass didn‘t get hot and survived the process.
To get a more even surface, I used 400 grit sandpaper on a solid and flat surface and some 15 minutes of musclepower.

The surface was like polished at the end and showed no traces of grinding and were at the desired 90° angle all around.

[hefezelle]

Would a tile cutter work, I have one that has a water tray, not used it for years but I’m sure it has a diamond disk but unsure it will work like a disk sander (cutting on the side of the disk not the thin end?

If there's a gritty coating on the side of the disk, that would very likely work, yes. But i doubt that, most likely the diamond dust will only be on the thin edge, no? The integrated water cooling from a tile cutter would be nice feature though!

I tightened the nuts a bit, but beeing afraid the glass would break under too much pressure, [...]

Glass almost never breaks from pressure, but from pulling tension. It can take about 100 times the compression compared to the tension it takes to break it. As long as pressure is applied evenly throughout the piece, such that no expanding tension is created somewhere else in the glass, it can withstand a shitton of abuse.

[thecroweater]

Yeah look, those sighties are designed for that type of O ring so I would suggest to address concerns you have maybe wrap them in thread seal tape

[Jason1979]

Hi Guys, thanks for all you help on this one, but I did cheat a little... I had the glass ground in a specialised lathe designed for borosilicate glass tube used in the petrol chemical and pharmaceutical industry, a local company to me, cheap and quick so was a no brainer.

Amazing factory and amazing seeing glass produced and formed, made me think how boring my own 9 till 5 is lol, anyway check the couple of photos and once again thanks for the hints and tips.