Now that we have the ballast neatly placed between the ties and not on top of them, we need to fix it with some sort of adhesive.
The traditional material is good old PVA white glue, diluted with a bit with water. You mist the ballast with so-called “wet water” and then dribble on the solution to soak the ballast and then let it dry. Various tools can be used to apply the mixture, but the slickest is a rubber ear syringe as it holds plenty, and is very easy to control.
Wet water is another area of great debate, as the traditional wetting agent is dish washing liquid, but Isopropyl alcohol (IPA) or Kodak Photo-Flo can also be used. The simplest for me is the automatic dishwasher drying agent liquids, as it is just a surfactant and does not contain and real cleaning agents. I use 1/4 teaspoon in 32 oz or one litre, based on an article online somewhere by Joe Fugate.I did try to mix white glue with IPA and it formed a gooey blob and did not dissolve at all. I am not sure how well it will dissolve in a water – IPA mixture, so I don’t use that.
In recent years the press has been talking about using artist’s acrylic matte medium instead of white glue, as it is not as water soluble after it dries. This all sounded good to me, and I had been using it to fix the main ground foam scenery on the layout. When it came time to do the track ballasting, it was supposed to work there as well, so I used that. Well, at least for me, this was a big mistake. No matter how much I tried to soak the sand to make sure the solution penetrated throughout the material, it ended up very fragile and crumbled very easily. Not what you want on your track work! So, of course, more controlled tests.
I tested fixing small piles of sand on a wood base without any track to prove a point. Even with the sand completely soaked with wet water and then mixed thoroughly with matte medium mixture to the point that it was a slurry, it still didn’t hold.
By the next day, after it had completely dried and look good with no visible glue residue, it still easily crumbled with the press of a finger.
So, back to try the old trusty Elmer’s While Glue and water. Cutting to the chase, after repeating the exact same process, this time it resulted in a very strong bond that could not be broken with a finger. There was no hint of a white residue as some have reported with white glue. As for any residual shine, I did another controlled test to see how shiny the white glue really was. When using matte medium, it is recommended to mix it with water and then let it stand for about a week to let the white powder settle out. This is reported to be talc that gives the medium its flat finish, however it can also leave a white residue behind, which we don’t want. The interesting thing is that once you separate out the white powder, what remains is just the clear acrylic medium, and it is glossy. So as a friend said, why not just start with gloss medium and save the extra decanting step. So, I tested both decanted matte and gloss medium and found both to be weak at bonding the ballast. As to their shininess, I let puddles of all three materials dry on a dark coloured plastic lid.
Surprising to me, the decanted matte medium was the shiniest, followed closely by the gloss medium, and then the white glue. The glue looked positively matte in comparison to both of the acrylic mediums.
I then did a small section of track to prove out the white glue approach, and while it looks awful when wet, it dries perfectly clear with no residue nor shine.
So, I am concluding that the white glue approach is still the best, in spite of more modern materials.
One caveat that I should mention is that the glue I am using is the original, standard Elmer’s “Glue-all” white glue. I have no idea if the results will be the same with any other brand of white glue. I’ll leave those tests to someone else.