06-30-2010, 10:30 AM
I used Liquitex when I first started ballasting and didn't have that problem, although I used a roughly 1:1 mixture of water and matte medium, about the same as for white glue. I don't put any detergent in the mixture, although I do saturate the area beforehand with water that's had a few drops of detergent added.
The problem could also lie with the dirt used. For the very first area on my layout that had ground cover applied, I used some very fine dust that I'd collected from work - just dirt that had been pulverised by hundreds of trucks, really. While it otherwise looked fine when dried, it also had white deposits on its surface. The results were the same using either white glue or matte medium, so I concluded that the problem was with the dirt. I looks great in the bottom of gondolas, which is now its only use, but I leave it un-glued.
For ballast or ground cover, I prefer white glue over matte medium - coverage is similar for both products, but the white glue is significantly cheaper. The finished appearance is the same, and I don't notice any sound quality differences, as some claim, between the two. The issue of water insolubility on most layouts would be a drawback, as major track changes usually suggest soaking the area with water to soften/loosen the ballast before lifting the track.
Unless your layout is in an excessively damp area, I doubt that humidity will have any effect on your handlaid track. Even if you do subsequent scenery work near the track, as long as you don't disturb anything while the area is wet, your track should survive just fine: after all, you've already soaked it once to do the ballasting, right? 
Wayne
The problem could also lie with the dirt used. For the very first area on my layout that had ground cover applied, I used some very fine dust that I'd collected from work - just dirt that had been pulverised by hundreds of trucks, really. While it otherwise looked fine when dried, it also had white deposits on its surface. The results were the same using either white glue or matte medium, so I concluded that the problem was with the dirt. I looks great in the bottom of gondolas, which is now its only use, but I leave it un-glued.
For ballast or ground cover, I prefer white glue over matte medium - coverage is similar for both products, but the white glue is significantly cheaper. The finished appearance is the same, and I don't notice any sound quality differences, as some claim, between the two. The issue of water insolubility on most layouts would be a drawback, as major track changes usually suggest soaking the area with water to soften/loosen the ballast before lifting the track.
Unless your layout is in an excessively damp area, I doubt that humidity will have any effect on your handlaid track. Even if you do subsequent scenery work near the track, as long as you don't disturb anything while the area is wet, your track should survive just fine: after all, you've already soaked it once to do the ballasting, right?
Wayne