Descaling Solution - Generally, a flush through descaler uses about .5 to .75 fluid ounces (1 to 1.5 tablespoons, or 8 to 12 grams) of citric or tartaric (grape) acid powder dissolved in 1 liter of water. This is a 2.25% to 3.5% solution, equivalent to 33% to 50% dilute lemon juice. Cleancaf and other coffee manufacturers' descalers use this formula. Theoretically, these amounts will dissolve about 12 to 18 grams of scale per liter, but that would require leaving the solution in for several days; in practice, it is used for an hour or two to dissolve up to 5 grams of scale.
The formula is mild enough to be harmless to espresso machine components, but it will come out of brass or copper machines with a slight greenish tinge. This comes from milligram levels of dissolved copper and is no cause for alarm.
Five pound bags of citric or tartaric acid cost about $10 at home brewers' or soapmakers' supply stores. This is roughly a 20 year supply.
Descaling Intervals - Know the hardness of the water you're using, and how much you use the machine. Descale when accumulations are between 2.5 and 5 grams. More often is a waste of time, less often may result in scale build up. Check out section 1.7 for instructions on determining your set up's scaling rate.
Single Boiler Machines
For single boiler machines, preventive descaling is no problem, just follow the instructions given by the manufacturer. In general, this involves filling the boiler, letting the solution work for about ten minutes, and replacing it by running it out of the steam wand under pump pressure. This procedure is repeated three to five times, until about a liter of descaler is used up. Then the machine is flushed with water until any taste is gone.
ChrisC wrote:Question is, considering that our water is kind of hard, and it's been a while, should I leave the descaler in the boiler for longer periods of time, or run two packages of descaler through, or anything like that?
And seeing as I don't think my Silvia has a chromed GH interior (I'm thinking of Jim's warning in the thread about descaling HXs), can anyone think of any reason I shouldn't do my regular backflushing and removal and cleaning of dispersion screen, etc., with JoeGlo right afterwards? Is it unnecessary, because the descaler cleans this too?
Come to think of it, is it better to remove the dispersion screen and that big chunk of brass under it during this process, in case any chunks of scale come out? (I know I'd have to be aware of the crotch-directed water jets if I did, though.)
ChrisC wrote:Thanks Jeff! Do you replace the screen and jet breaker before running the descaler through the machine, or do you leave them soaking while you do that? I'm not sure what to expect in terms of the scale coming out -- is it completely dissolved in the descaler? Is it a fine powder, or even small chunks, which could get caught in the inside of the screen if it's left on?