How to Ballast Track
Not only does ballasting track make it look realistic, but it also helps keep it firmly in place. One of the most important things to do when ballasting track is to make sure that the ballast is firm and that the inside of the rails are free from material to ensure smooth operation and to keep ballast from getting stuck in the gears of your locomotives.
Here are basic instructions that are applicable for all scales.
What you need:
50/50 mixture of rubbing alcohol and water in a spray bottle
Cup or spoon for spreading ballast
Diluted Elmer's white glue (I use approx. 40% glue 60% water
Step 1) This is an extra step I take for maximum adhesion. Take a paintbrush, dip it in your diluted glue, and paint it onto the sides of the cork or whatever type of roadbed you're using.
Step 2) Use a spoon, cup, or other object to pour some ballast evenly down each side of the track. Pour small amount of ballast down the center of the track. Do this in sections rather than trying to ballast the entire layout in one shot.
Step 3) Use a dry paintbrush to spread the ballast. Keep the ballast below the ties. I use a computer keyboard vacuum to vacuum up any excess ballast that I don't want glue in place.
Step 4) Use a spray bottle with a 50/50 mixture of water and rubbing alcohol to saturate the ballast.
Step 5) Use an eye dropper or other method (I use an old Oxy 10 bottle) to drip the glue mixture onto the ballast. Be sure to cover it completely. Don't drop it from too high or it will displace the ballast. If you didn't use enough of the rubbing alcohol spray then the ballast will bead up and form a ball. This also means that the ballast underneath in that area didn't get wet and will not receive the glue. If this happens just spray the area with more rubbing alcohol mixture until it's saturated. Give the glue at least 24 hours to dry
Step 6) Use an X-Acto knife to go along the inside of the rails and remove any glue dried on the rails. Also loosen any bits of ballast that will interfere with the train operations and any other ballast you don't want. Use a track cleaning eraser to clean glue off the tops of the rails. This is the step where you'll feel like a dentist cleaning plaque off of someone's teeth.
Step 7) Go over the area with a vacuum. And loose ballast will get picked up. If an area did not receive enough glue it will also get lifted up. You can patch these areas later using the same process.
Step 8) Go over the newly ballasted are with an old train car. Repeat steps 6 and 7 for any areas where you feel the train car bumping along the rails.