mathof2 Oh good point above. Did you follow the instructions and use a 5ml sample or get a 20ml sample for better accuracy?

Also did you stop the test at the first sign of colour change or continue until there was a “bright” colour? The former is what you need to do.

      Rob1 Oh good point above. Did you follow the instructions and use a 5ml sample or get a 20ml sample for better accuracy?

      Also did you stop the test at the first sign of colour change or continue until there was a “bright” colour?

      I drew off about 40mm into a beaked measuring jug, and poured 5mm samples from that into the supplied test tubes.

      I stopped soon after the first faint sign of colour change, but perhaps I went a drop too far.

      I will re-do the tests on the coffee infusion samples and do new ones on the pure RO water, and report back.

      Thanks to all for your assistance.

          mathof2 Rob1

          Here are the latest measurements (ppm):

          RO water: GH 35.8 (2 drops); KH 35.8 (2 drops); total TDS 46 (meter)

          Coffee minerals: GH 89.5 (5 drops); KH 53.7 (3 drops); total TDS 98 (meter)

          Tap water: total 199 (meter)

          Question: could it be right that the total measured-by-meter TDS of the samples is greater than the total minerals in the samples measured by drops?

                mathof2 Question: could it be right that the total measured-by-meter TDS of the samples is greater than the total minerals in the samples measured by drops?

                TDS (ppm of everything in the water, as ion) and GH (calcium and magnesium only, multiplied by known factors)/KH measurements (ppm as CaCO3) are not in common units, forget the TDS.

                    mathof2 I haven’t and you don’t need to either 😀

                    Just stick to the meaningful units.

                    GH & KH relate to scaling potential and alkalinity (KH) in the water, KH also affects perceived acidity in the coffee produced (more alkalinity/KH = less acidity).

                    TDS is anything in the water, organic & inorganic, much of which has little to no effect on what we are interested in.

                    Course completed. Look at it as ingredients rather than ‘science’.

                      mathof2 Ok what I’m trying to understand here is what the RO water is. 35.8mg/l GH/KH seems high.

                      So as has been touched upon above a 20ml sample will give better accuracy. With a 5ml sample, when the colour changes with two drops you know the GH/KH is somewhere over 17.9mg/l and below 35.8mg/l (range between drops is 17.9mg/l). With a 20ml sample the range between drops will be 4.475mg/l….so the test is much more accurate with a larger sample.

                      Right now your RO is 17.9-35.8mg/l GH/KH and your remineralised water is 71.6-89.5 GH and between 35.8-53.7 KH….so the infusion adding 10.8 KH might be right. Weird formulation adding only 10mg/l alkalinity to supposedly highly pure RO water.

                          Rob1 Weird formulation adding only 10mg/l alkalinity to supposedly highly pure RO water.

                          It would only be highly pure if a DI resin filter was used (no mention of that).

                            Now I understand what is meant by a 20ml sample (each drop to be multiplied by 4.475O). I’ll use that method tomorrow and post the results.

                            I have a worry that the RO water is being contaminated by a leak from the remineralisation bottle. The TDS readings on the RO water went up when I first added a remineralisation bottle to the machine, and have stayed up. I know Skuma has identified such leakage as a possible problem. But given that such leakage would be only of wanted minerals, I don’t know if it matters.

                            Rob1

                            Here are the measurements taken with 20ml samples:

                            RO water: GH (7 drops) 31.325 mg/l; KH (6 drops) 26.85 mg/l

                            Coffee infusion: GH (12 drops) 53.7 mg/l; KH (7 drops) 31.325 mg/l

                            I hope that tells you something useful.

                            Thanks again for your advice.

                            Best wishes,

                            Matt

                            • Rob1 replied to this.

                                mathof2 well it changes things significantly. How hot does the Londinium run?

                                  The boiler peaks a 1.4 bar, which according to a superheated steam calculator on the internet is 126.254C.

                                  By the way, the taste of espresso made with the Skuma coffee water is delicious. It’s at least as good as the Volvic I used previously, perhaps better as it seems somehow more transparent in revealing the flavours of the beans.

                                    mathof2 if you can make proper rodi water with zero tds, try the Dr pavlis water

                                    It uses potassium bicarbonate, will never scale, and I find you get the true bean, the water adds nothing

                                    Decent De1pro v1.45 - Niche Duo - Niche Zero - Decent is the best machine ever made -

                                      mathof2 ok no need to descale the HX, flushing of the boiler regularly is going to be necessary to prevent scale build up or just schedule descaling. IIRC volvic has about twice the alkalinity of the water you are now brewing with so will mute the acidity much less which goes some way to explaining the difference in results.

                                        I guess I’d rather flush the boiler regularly than bother with descaling.

                                        It’s a relief to know that I can just go ahead with the system I now have.

                                        Buon caffè a tutti!