Thankyou very much for providing such useful information on how to deal with exposed brass!
How acidic would something have to be to be considered strong in this case?
e.g. espresso acidic or a cleaning product like vinegar, etc?
Thanks

Strong acids like sulphuric and hydrochloric will quickly strip the oxide coatings off copper and its alloys. With brass, a copper-zinc alloy, strong acids will attack the zinc in the alloy. Copper itself does not react with acid directly, but acid removes the oxide coatings and then elemental oxygen can attack it. In the presence of things that complex copper, air oxidation can become extremely rapid.

Weak acids like acetic acid will take time to react, but they will react a lot more rapidly at higher temperature. One should be especially careful with machined leaded brass, because even relatively weak acids may leach out lead.

Oddly the pH that tends to result in maximum metallic stability for brass and copper is very slightly alkaline--what one gets with low concentration of bicarbonates. This keeps the oxide coat intact. I try to avoid any conditions that produce scale both for chemical safety and for flavour. Copper is required for life, but it is also toxic in over doses. Lead is always toxic.

Brewed espresso is a bit acidic. If one take care to safeguard oxide coats on portafilters by avoiding abrasive cleaners, and also rinsing them with clean water immediately after use, there seem to be a lot less problems with foul tastes. Again I think it wise to avoid polishes and abrasive cleaners on surfaces that espresso will contact. I think without soap, but rinse them well.

Starting to wonder If the issue stems from my use of R.O. water.

(ciao from Sicilia btw)

Check the Ph of your water. Buffering may be required.

Any recommendations for a Ph meter.
After a week of testing and using 50% spring water and 50% R.O. the issue has subsided dramatically.

Coffee oil is composed of 46% linoleic acid, this acid will oxidize and results in a rancid taste.
A residual film of oil if left on the brass surface makes for an ideal environment for accelerated oxidation.
Contributing factors include elevated temperatures, the presence of copper acts as a catalyst and breakdown products from oxidation will accelerate further oxidation.
So daily cleaning is necessary.

redbone wrote:Any recommendations for a Ph meter.
After a week of testing and using 50% spring water and 50% R.O. the issue has subsided dramatically.

Most consumer grad Ph meters are less than precision instruments. This Ph Tape is standard lab use and is more than adequate for this task. https://www.amazon.com/Micro-Essential- ... ds=Ph+tape Should be available north of the border as well.

Great and thanks, will search for it here.

If you store it in an air tight bag and cool out of direct sun that tape will last for a very long time.

Order placed. Cost $8.39cda delivered. Estimate 2-3 days.