I found some old bottles, some glass and some stoneware, which had been in a river, and dredged out and lain in a dump for years, and had limescale and brown iron staining on them.
I washed them first, to get rid of the mud.
To clean the limescale and staining off the outsides, I poured Harpic toilet cleaner on them and left it a few hours, then scrubbed with a toothbrush and more Harpic. Harpic contains hydrochloric acid and dissolves the limescale.
To clean the insides, I put grains of wheat in them (you could use rice or small beans instead) and more Harpic, and left them for a few hours. Then give them a good shake and the movement of the wheat helps the Harpic shift whatever's inside.
This is good for the Codd bottles that have a marble inside the neck, making it difficult to get a bottle brush into the bottle.
When they are clean, tip the Harpic and wheat away, give the bottles a good rinse out, and then soak them in a solution of bicarbonate of soda to get rid of the acid.
Then another good rinse and you will have beautiful clean sparkling bottles.
The Harpic wasn't so good with the stoneware bottles, and if left too long it will stain the stoneware blue.
One of the bottles had tar deposits inside it, I soaked the bottle in white spirit for 24 hours and was then able to scrape the tar out and the last little traces of it dissolved.
Word of warning: Harpic does horrible things to metal - it made a mess of my stainless steel draining board, so do the cleaning operations in plastic bowls and on newspaper.
I hope you have found this helpful, please vote YES for me at the bottom of the page.
Happy hunting from Mandy.