After being ejected out of a volcano, grey cinder/volcanic rock gets its appearance from the simultaneous rapid cooling and depressurization process. Grey Cinder Sand has small cysts, which is what causes it to be so light in weight. We crush it down to make 138 CSX SP Wabash Grey Ballast.
Cut a corner off the package and sprinkle it out with a shaking motion parallel with the roadbed. Begin at the base of the roadbed slope and apply in layers as you work your way up to the top. Do this for the other side as well. Apply a thin amount around the ties. Spread the ballast around the ties with a 3/8” brush. wipe the ties clean with your finger. Tap the rails with the brush handle to bounce the rock away from the rail flanges. If necessary, groom the sides by dragging a piece of paper. Wet the ballast with wetted water through an eye dropper and drip only on the ties at first. Now bond the material with a mixture of one-part white glue and two parts water with eye dropper the same way.