NOTE: I slightly edited this post and my latest reply on 9/2 has more detail to hopefully convey exactly what this looks like.

OMG--I bought some citric acid from a well-known Indian spice store in NYC (Manhattan). It was labelled "Lemon Salt" and the bag also said on it: "Also known as Citric Acid or Sour Salt"--I confirmed elsewhere that all 3 names are interchangeable. It said it is used to keep foods from changing color, etc. So I am positive it was "food grade."

The grains were rather coarse in size but I was able to almost completely dissolve them (I think maybe some tiny sand-grain sized particles may not have fully dissolved) in warm or hot water before running the solution through my Gaggia Classic. I went easy on the amount. I only put one Tablespoon per liter in a 2L tank of water. After the descale process, I ran a full 2 tanks of water through the machine--even though one is usually considered enough. I then tasted the water and it did not taste acidic/lemony/etc.

Bottom line is: that was 10 days ago. I even backflushed the machine with Joe Glo 4 days ago, but I continue to see a residue floating on top of the water if I run water into a cup through the grouphead or the steam wand. It is most evident when the machine is fully heated.

What have I done or what can I do to clean this out? (I assume the residue is from the citric acid b/c I never had it before that descale day.)

Thanks in advance--all feedback is appreciated.
EG

Could be due to the aluminum boiler?

AFAIK, aluminum accumulates aluminum oxide which is not dissolved by the citric acid.

Either disassemble and flush or flush lots and lots.

Hi,

Can you clarify a little? Do you mean that citric acid did something to the boiler? Do you think that is aluminum oxide residue? This machine is supposed to be fine with citric acid even in the aluminum boiler...

Your solution concentrate was too light and most likely just started to break the scale loose. Use 2 tbs per liter and let it sit in the heated boiler for 30 minutes then flush. How long between descaling has it been?

About 2 months from when the machine was new.

Gime2much wrote:Your solution concentrate was too light and most likely just started to break the scale loose. Use 2 tbs per liter and let it sit in the heated boiler for 30 minutes then flush. How long between descaling has it been?

It was 2 months from when new. Are you saying the residue I see is probably scale? But even if it only partially broke down the scale, wouldn't the scale that came off have been flushed away already?

One sure way to find out. Descale again with the 2 tbs/liter mixture.

iirc, you should NOT use the citric acid solution on a machine with an aluminum boiler. Verify the material that the boiler is made of before proceeding and do some research as to the correct chemical to use for that machine. Citric Acid and related commercial products such as that are fine on stainless and brass (and copper?) but not for aluminum iirc.

Randy G. wrote:iirc, you should NOT use the citric acid solution on a machine with an aluminum boiler. Verify the material that the boiler is made of before proceeding and do some research as to the correct chemical to use for that machine. Citric Acid and related commercial products such as that are fine on stainless and brass (and copper?) but not for aluminum iirc.

But the people who run the Gaggia group on Yahoo insist that citric acid IS fine to use and that it will not harm the aluminum boiler. They claim to be very tight with the US distributor as well and apparently base their statements on convos with the distributor / tech dept.

They state that the 2 Tbsp citric acid per liter H2O is correct amount for these aluminum boilers.

What makes you say it shouldn't be used on those boilers? What would happen, and do you have some idea why my water keeps having white residue now? I would definitely like to know and I like to hear all sides on these things--you see how confusing this all is for the consumer...

What chemical do you suggest for aluminum if citric acid is not right?

Thanks.

Sorry Randy, Better check with the hundreds (thousands?) of Gaggia owners that have been using citric acid for years with no noticeable bad effects. Just another urban myth.