Iris is made of stainless steel and polished Brass. Brass will naturally patina when used but this can be easily be cleaned off if you prefer the polished look.
To clean the rings of Iris we recommend being very careful because it can interfere with the tightly machined tolerances if done incorrectly.
Start by taking some Brasso wadding (or other brass cleaning agent), this can be purchased at most hardware stores, supermarkets, and online. Take a small piece of the webbing and in small circular motions wipe the brass ring. Try to not let any of the cleaning agent into the splits and joints of the Iris because this can attract dirt and grime. The wadding will change colour becoming black as it picks up oils and residues from the brass.
Once you have cleaned the brass take a soft cloth or tissue and slightly moisten it with some water and washing up liquid/soap. Then wipe off the residue from the Brasso in a similar motion and care to the Brasso webbing. Finally taking another soft cloth/tissue and dry any moisture on the top of the Iris.
By now your Iris should be back to its polished self and may have even removed some micro scratches.