The hardness in all Third Wave Water (TWW) mineral packets is permanent hardness. If it is in a glass and the water evaporates, there will be minerals on the inside of the cup. The difference between it and temporary hardness is that those minerals left behind are still water soluble, any new water in the glass will re-dissolve the minerals.
If any temporary hardness (carbonate hardness) gets deposited on the steam coil it will not be re-dissolved by water. This scale will need to be dissolved by a chemical descaling agent.
To verify how TWW would react I ran nearly 70 steam cycles at 60 seconds intervals, condensing the resulting steam and measuring the volume (mL) and TDS of the condensate. All tests and the results are available in this spreadsheet. In the spreadsheet there are also links to the screenshots from 48 of the steam cycles.
Clean steam coil:
If a cycle of dry steam leaves minerals behind in the steam coil, then any subsequent wet steam cycle will re-dissolve the minerals left behind. The steam coil after this wet steam cycle is what I will refer to as a “clean steam coil.”
Mineral retention in a clean steam coil:
I found TWW had zero evidence of mineral retention inside of the helical steam coil between the steam flow rates of 1.2 mL/s - 2.5mL/s. With my specific Decent machine, the flow rate of 0.8mL/s was the driest flow rate with only about 40-50% of the original TDS showing up in the condensate during the first clean cycle.
Self regulating maximum mineral retention:
If multiple dry steam cycles are performed one after another, subsequent dry steam cycles leave less and less minerals behind. Most likely this is a layer of minerals reducing the thermal efficiency of the steam coil, causing the steam to be wetter. This wetter steam then re-dissolves some of the minerals pushing them out thus creating a maximum amount of minerals that can be retained.
Steam Flush Cycle:
If your desired steam flow rate is less than 1.2mL/s and you want your steam cycles to be as accurate as possible. Then I would recommend periodically running a 2.5mL/s steam cycle for 30s to flush any retained minerals out and leave the steam coil in a clean state.
Decent Espresso DE1XL 110VAC
300mm glass Graham condenser
300mm glass Vigreux distilling column
1000ml 3 neck round bottom flask
¼” ID x 3 feet Silicone tubing (connect steam wand to top of condenser)
⅜” ID Silicone tubing 10 feet (chiller to the condenser)
Glass straight inlet adapter
CW-3000 water chiller
250ml graduated cylinder (+/- 2ml accuracy)
HI99300 Hanna TDS Meter (+/- 2% accuracy)
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