Demijohn unable to clean.

[An Ankoù]

Que! Etched?

It's like "Itched" but with an E.

It happens when the surface of the glass is eaten into by whatever eats into glass. Not HF, I hope!
I cleaned a borosilicate glass flask with strong bleach and left it there for ages. Never did manage t get the milky sheen ff the inside.

 

[foxy]

Hadn't realised that was an option. But looks that I can only get this online. 1kg sems most cost effective, but not sure I'd ever use that amount.
Sodium tetraborate (borax) seems easier to obtain, would that be be worth using?

I buy mine in 25 kg bags, it is more stable than sodium percarbonate. I think I read that sodium perborate may not be available in the UK.

 

[MartinF]

The good old fashioned method that was recommended and that I used to use in my winemaking days, was to swirl a length of lamp chain around with some water or cleaning solution. So you have both mechanical and chemical cleaning methods. It's also good for the arm muscles. For the younger people here, "lamp chain" is a lightweight, typically chrome plated brass chain, with links around 5-10mm. Sometimes used as bath plug chain. Good hardware stores should (still) sell it.

 

[Chippy_Tea]

I am sure i have read people used to use marbles to swirl around the inside of the DJ to help clean it.

 

[MashBag]

.. And sand

 

[MashBag]

With TFR

 

[moto748]

The good old fashioned method that was recommended and that I used to use in my winemaking days, was to swirl a length of lamp chain around with some water or cleaning solution. So you have both mechanical and chemical cleaning methods. It's also good for the arm muscles. For the younger people here, "lamp chain" is a lightweight, typically chrome plated brass chain, with links around 5-10mm. Sometimes used as bath plug chain. Good hardware stores should (still) sell it.

I'd echo that, and add that unplated brass chain (if you can get it) is much better than plated.