Glass tube polishing. Boiler sight glass replacements

#1: Post by **redbone** » March 24th, 2017, 3:27 pm

I decided to get some glass tube and have them cut from a laboratory supplier for the La Pavoni lever machines..
Received a bunch of glass tubes cut to size but found the ends need some polishing.
Any suggestions regarding polishing. Has anyone done fire polishing. Is it recommended ?

#2: Post by **ira** » March 24th, 2017, 6:58 pm

Fire polishing will tend to make the end smaller but you have enough I'd try one. I think a gas stove might be hot enough. Make sure to turn the tube while heating it so it's doesn't sag. Otherwise a small diamond ile or wet dry sandpaper will let you take the sharp edge off.

Ira

March 24th, 2017, 9:25 pm

Will try this weekend.

Thanks Ira

#4: Post by **gtemkin** » March 24th, 2017, 10:43 pm

What kind of glass did you ask for? If they gave you borosilicate glass (Pyrex) you probably would need more than a stove flame to fire polish the ends. If they gave you a soda-lime or lead glass then you could use a stove flame but I would suggest using Pyrex for something intended for temperature excursions like a boiler sight tube.

March 24th, 2017, 11:03 pm

Manufacturer states clear "hard" borosilicate glass 3.3 which excel in high heat and chemical resistance defined by international ISO 3585 Standard and Type I Class A glass of ASTM E438.
http://www.kavalier.cz/en/section/15-ge ... ation.html

#6: Post by **gtemkin** » March 25th, 2017, 12:01 am

That's the right stuff. Think you'll need a proper torch/burner for fire-polishing. Propane or MAPP torch should work.