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Date: 01 Jan 2007 08:09:29
From:
Subject: Is scale a protective coating?
I opened up the boiler of a 25-year-old Gaggia for descaling, but don't
know
what to do next. The top-half of the boiler (aluminum) is coated with
a thin layer of something that is dark, almost black, and bumby,
and dry (not slimey).

Is it scale or corrosion?

Should I try to scrape it off somehow? Should the inside of
a boiler be shiny? Or maybe I should leave it alone?

Here are a couple of pictures of the boiler insides:

http://img523.imageshack.us/img523/2669/boiler008fu5.jpg
http://img216.imageshack.us/img216/6292/boiler001jy8.jpg

Here is a picture of the machine itself, a gaggia baby:

http://img213.imageshack.us/img213/4059/baby001uc3.jpg

Thanks,
John





 
Date: 02 Jan 2007 16:44:32
From: daveb
Subject: Re: Is scale a protective coating?
just clean the sealing surfaces.

and make a bead in the brewhead channel -- brass portion -- that it
about 1/8 in. higher than the surrounding area and let it cure
overnite.

then screw it together.

dave



  
Date: 03 Jan 2007 01:18:07
From: Robert Harmon
Subject: Re: Is scale a protective coating?
I'd suggest folks read & follow the directions on the sealant package rather
than take daveb's word about anything.

Robert (Never take advice from one who stands to profit from your mistakes.)
Harmon

"daveb" <davebobblane@gmail.com > wrote in message
news:1167785072.091321.144580@i12g2000cwa.googlegroups.com...
> just clean the sealing surfaces.
>
> and make a bead in the brewhead channel -- brass portion -- that it
> about 1/8 in. higher than the surrounding area and let it cure
> overnite.
>
> then screw it together.
>
> dave
>




 
Date: 02 Jan 2007 12:38:04
From:
Subject: Re: Is scale a protective coating?
Thanks for the opinions and advice so far, I was not looking forward to
scraping it clean!

I picked up some RTV silicone this afternoon (Dow Corning 736
heat-resistant silicone sealant,
http://64.242.109.170:8080/1/doc?id=26149), hopefully it will do the
job. It is rated 500F continuous and is NSF listed.

John


Jack Denver wrote:
> I think what you are seeing is basically the surface of the aluminum, made
> pitted and rough thru minor corrosion. There is a light coating of
> oxide/scale but not enough to interfere with the operation of the machine
> and yes it in effect seals off the raw aluminum. I'd maybe wire brush the
> interior a little to remove anything loose and wash with a strong detergent
> (TSP) , but basically I'd leave it alone. Don't try to get down to shiny
> metal, except in the gasket seating area. This boiler (the casting is
> impressively thick) has made in thru 25 years and should make it thru
> another if you don't mess with it too much. When puttting it back together,
> in addition to the gasket I'd add a layer of hi-temp silicone caulk to be
> sure of the seal.
>
>
> <jb130@mail.gatech.edu> wrote in message
> news:1167667769.933829.246000@48g2000cwx.googlegroups.com...
> >I opened up the boiler of a 25-year-old Gaggia for descaling, but don't
> > know
> > what to do next. The top-half of the boiler (aluminum) is coated with
> > a thin layer of something that is dark, almost black, and bumby,
> > and dry (not slimey).
> >
> > Is it scale or corrosion?
> >
> > Should I try to scrape it off somehow? Should the inside of
> > a boiler be shiny? Or maybe I should leave it alone?
> >
> > Here are a couple of pictures of the boiler insides:
> >
> > http://img523.imageshack.us/img523/2669/boiler008fu5.jpg
> > http://img216.imageshack.us/img216/6292/boiler001jy8.jpg
> >
> > Here is a picture of the machine itself, a gaggia baby:
> >
> > http://img213.imageshack.us/img213/4059/baby001uc3.jpg
> >
> > Thanks,
> > John
> >



 
Date: 01 Jan 2007 13:10:10
From: Jack Denver
Subject: Re: Is scale a protective coating?
I think what you are seeing is basically the surface of the aluminum, made
pitted and rough thru minor corrosion. There is a light coating of
oxide/scale but not enough to interfere with the operation of the machine
and yes it in effect seals off the raw aluminum. I'd maybe wire brush the
interior a little to remove anything loose and wash with a strong detergent
(TSP) , but basically I'd leave it alone. Don't try to get down to shiny
metal, except in the gasket seating area. This boiler (the casting is
impressively thick) has made in thru 25 years and should make it thru
another if you don't mess with it too much. When puttting it back together,
in addition to the gasket I'd add a layer of hi-temp silicone caulk to be
sure of the seal.


<jb130@mail.gatech.edu > wrote in message
news:1167667769.933829.246000@48g2000cwx.googlegroups.com...
>I opened up the boiler of a 25-year-old Gaggia for descaling, but don't
> know
> what to do next. The top-half of the boiler (aluminum) is coated with
> a thin layer of something that is dark, almost black, and bumby,
> and dry (not slimey).
>
> Is it scale or corrosion?
>
> Should I try to scrape it off somehow? Should the inside of
> a boiler be shiny? Or maybe I should leave it alone?
>
> Here are a couple of pictures of the boiler insides:
>
> http://img523.imageshack.us/img523/2669/boiler008fu5.jpg
> http://img216.imageshack.us/img216/6292/boiler001jy8.jpg
>
> Here is a picture of the machine itself, a gaggia baby:
>
> http://img213.imageshack.us/img213/4059/baby001uc3.jpg
>
> Thanks,
> John
>




 
Date: 01 Jan 2007 08:23:14
From: daveb
Subject: Re: Is scale a protective coating?
Wow -- it looks GREAT inside. do nothing!

just make sure the sealing surfaces are smooth and clean. you'll need
a new gasket (o-ring) and make sure it heats up -- if it does not, you
are basically SOL

Dave



 
Date: 01 Jan 2007 08:15:37
From:
Subject: Re: Is scale a protective coating?
bumby = bumpy