Just a bit lightweight to be "serious" preservation, but something to see--the removed gauge glass from SP No. 2248, courtesy of Hayley Enoch and Railroad Glory Days (Facebook site):

https://fbcdn-sphotos-c-a.akamaihd.net/ ... c57f470f67

And the commentary, first from the site administrator:

No article today, just a cool picture. Recently the mechanics replaced the glass in the 2248's sight gauges. This is the old glass. It's thicker than you would think--more than 1/2".

And the following comments:

John Gregory: We used to find that the steam and heat scoured the glass thinning quite drastically. These are Klinger glasses and even on the RH & DR they were about 3/4 inch thick when new. Scale does not really build up on the glass but it will on the metalwork of the frame (the glass holder). To prevent this build up you have to 'blow' the frames down once or twice a day. Gauge Frames can be isolated should the glass fail when in use, it is very scary when they do let go but they should not sideline the loco as they (except the GWR in the UK) generally have two frames. I personally have changed a goodly number of these as they would last two years on the RH & DR whilst running at 180 psi in the boilers.
Like · Reply · 2 · 2 hours ago

Hayley Enoch The crew will generally blow them down several times during running. The scale had most definitely built up on the glass though, it was getting hard to see the water. I think these were just old enough to need new glass no matter how well they could be cleaned. This loco has two glasses (This is federally required in the US IIRC). The engineer's side is the slightly shorter one.
Like · 2 hours ago

John Gregory One of the 'things' we found that was the water treatment could, and did strip the glass and brass fittings of their lead content. That meant that after a few years we had to replace the entire gauge frame as the brass was too brittle and the glass had all but worn to a paper thickness. As an experiment we ran one loco without the chemical treatment and had regular blow-downs (we started doing that in 1993 on the RH & DR). The result was that the gauge frames were in better condition and the glass lasted longer. Interesting that you run different sized glasses. I have never come across that before, I certainly can not think of a Brit loco so set up.
Like · 2 hours ago

Hayley Enoch: I do not think that they were designed that way back in the day, I think it's something that is required by law now. I also do no think the gauges are made of brass (not sure what though.) They were not replaced at this time. I friended you & if you accept I can send you pictures of the whole cap setup. All in all though, I think it's better to keep the chemicals in there to protect the boiler and clean or replace these every so often.
Like · 25 minutes ago

John Gregory: We suffer from very hard water in Kent (UK), even after softening we needed to treat it. Once we started the boiler blow-down trial we found that the loco only needed a washout once every six to eight weeks as opposed to every week, that was without chemical treatment. Sadly I no longer have much to do with the line as I have moved on so to speak (Truck Driver now). I am very involved with the total ground up re-build of a 1917 Aveling and Porter Traction Engine, amongst other projects.
Like · 20 minutes ago

Lawrence Wartenberg: has to be thick at 200 psi plus boiler pressure ....would venture a guess that there are replaced account scale buildup inside makes it hard to see the water level..
Like · Reply · 2 · 3 hours ago

Hayley Enoch: Pretty much Lawrence and Robert, the glass was starting to get "frosty." I don't know when they were last replaced but it must have been quite a long time ago!
Like · Reply · 1 · 3 hours ago · Edited

Robert Cooper: I would surmise that Lawrence is correct about the water scale buildup. I use a CPAP machine for my sleep apnea. Even using "purified", bottled water, my humidifier tank will still need regular cleaning for scaling on the plastic tank. I can't imagine what it would be like with the water used in the locomotives.