Cleaning Stainless Steel Shot

[katzi]

Hi there,
I hope to get some advice on cleaning my steel shot. I left my shot in the tumbler covered with water but did not realise I had polishing compound in it too (barrel brite) The water had went brown and gungey but the shot seemed ok.
Cleaned everything up and ran the tumbler with the shot for a while then added some barrel brite and ran it again. Thought all was ok until I tumbled some copper findings and they came out as dull as they went in! I have since left the shot covered in water which has gone brown too.
I am thinking I have ruined the shot and need to replace it
I have read through a few threads on cleaning shot and suggestions of cleaning with coke or bicarbonate of soda??
The tumbler is from cooksons 999 6025 and the steel shot and compound came with it.
Many thanks in advance for any help!

Edited to add, the description on the starter kit describes it as mild steel shot.