I was in the trainroom a little while ago, working on a small area of scenery that had to be ‘glued’ down. I picked up a bottle of matte medium/ water mixture and gave it a spray. Good Grief, gag a maggot, it smelled like rotten eggs. I had no idea this stuff would go rank on a person. I found the original bottle of matte medium and gave it a smell and it’s fine, just the diluted stuff. A little egg nog at Christmas is fine…, rotten eggs… no way.
Jarrell
I have had the WS scenery cement do the same in an unopened bottle. Problem is, in a club setting this bottle could have been around for some time. The seal must have been broken to get that nasty. I never had it happen with matte medium, but as you say it was the diluted. Has to be bacteria introduced in the container or the water that causes it.
How long was the diluted bottle sitting around?
A couple of drops of Lysol will stop the growth of new chemical compounds. There is enough bacteria and whatnot in tap water to grow all sorts of interesting things when left alone and the Lysol or other disinfectnt will not only stop the bottles festering, but also stop similar growth on your layout (could be interesting if you want to grow your own swamp). J.R.
J.R.,
Good tip, forgot about doing something so simple. Used to add Lysol to wallpaper paste, but that was to stop mildew behind the paper.
I’ll have to remember the Lysol. I add a jigger of it when I mix Ground Goop, but never would have thought it necessary with diluted matte medium.
Live and learn! 
Jarrell
Even latex paint left in a can will grow mold.
Roger, at my age if I sit around too much I get the same way.
Jarrell
Had that happen a while ago. Funny thing that some diluted paint in a small jar from the same can was just fine.
I think I’ve got a dead mouse somewhere in the train building. Stinks pretty bad…
I always add some alcohol to my matte medium. Never had it get smelly.
A few drops of chlorine bleach may do the same as Lysol and be cheaper unless you already have a bottle of Lysol around.
That actually happened to me! A mouse died in the suspended ceiling above the layout. I smelled something for a few days but figured it was probably my old sweatshirt … Finally my wife mentioned it so I removed ceiling panels until the body was found. The cadaver was removed when it was rather badly decomposed. An autopsy showed the mouse died of boredom waiting for me to make more progress on my layout …
Dave Nelson
hmmm, now I have an excuse to start my layout…If I convince my wife that the money saved on mousetraps can be invested in the empire.