Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

I got my Wilesco D21 about 10 years ago. The first time or two that I ran it I used tap water. I started to get a little bit of fogging on the top of the sight glass. I assumed that it was a little bit of mineral deposits and thought it would dissolve using distilled water. It never improved but didn’t really get much worse. I was out of the steam hobby for a few years and it sat on the shelf. I got it out and started playing again a couple of months ago. I always would blowdown the boiler after a session and leave the gauge and whistle off. I had a long weekend a week ago and decided to just leave the water in it, since I was going to do a lot of playing. The haze got much worse, and is actually worse than you can see in the picture.It covers the whole glass, but is much worse at the top.I decided it was time to take the glass out and clean it. I washed it with soap and it did nothing. Next I used denatured alcohol and it did nothing. Time to break out the acetone and still nothing. I soaked it in my citric acid pickling jar for 12 hours and still nothing. Tried WD-40 and fine steel wool and still nothing. I decided it was time to put in my spare. What would cause this? The only thing that I can think of is some leftover flux from when they soldered the boiler. Anyone else ever have this and any ideas what caused it?

I always use decalcifier spray - that should work
Arnold

SiO₂ is pretty impervious to just about anything but hydrofluoric acid, which would etch it to where you'd feel the difference. If there was ever any HF in your boiler, it is unlikely that you'd still have a boiler.

It's not mineral deposits.  Steam etches glass. I work on steam heating systems and this is why we change boiler sight glasses.  I suppose if you like you can try polishing it with toothpaste and possibly clarifying it.