Hi All: I am draining my steam boiler again to get rid of the fluffy tan substance in the sight glass. This is the 3rd or 4th time over four months from new. Does anyone know what this is? I doubt it is a bio-anything due to the operating temperature but stranger things have been reported. I found cheap copper washers for the drain plug (under the sight glass) at Graingers (part # 5ZLT9) that work fine and were about $2 for 25 (about $.90 each from espresso parts places).

Limescale?

I would doubt that: machine is 4 months old, good water and double MC2 cartridges in filter system. I should have taken a picture but didn't think of that. I guess it will come back based on the history and I will take a snapshot then.
Duke

Question... what is the "sight glass?"

One of the beans we use at the cafe is from a roaster called "Sight Glass." I didn't know it was the name of a part...

sight glass (n): A transparent tube or window through which the level of liquid in a reservoir or supply line can be checked visually.

I get that all the time. I'm sure it's some sort of scale. I just continue to clean it when I get disgusted with it. One day I will finally descale my machine (it's over 7 years old without ever descaling).

Tried flushing, also shaking it up when cleaning and emptying the boiler (easier said with a La Pavoni)? I also flush most of a residual the boiler between shots and use a big 12x2" solid block, coconut-carbon filter attached to the sink faucet for all cooking or drinking needs. Wasn't much from Ebay, filter from one place, another for a big box of 12 5- or 2-micron filters off some RV outfit that went into an overstock condition. . .$50/60, altogether and spiffy for one-stage filtration results (no ground issues, cysts or microorganism, just the water stinks with City chlorine treatment). Seeing scale with a flashlite inside the boiler is bad enough, but don't think brown flotsam would be my cup of tea, either.

My Linea has it too. Have yet to go through with my first descaling of the machine, but it's about time now methinks...

In my Gaggia Factory, scale seems to like to build up on the nut that attaches the bottom of the sight glass to the boiler... so far no scale in the sight glass, but it is annoying.

I use a water softener cartridge and a water filter for my brew water.

it could be milk that gets sucked back up the steam wand if you shut off the valve too quick, and then do not get it purged sufficiently after steaming.

Eric