Ballast

[lenht1951]

So why is my grey ballast turning almost black after pva / water 50/50 mix has been applied and has dried.

[Bufferstop]

What IS your grey ballast? Your bag of little grey chippings can be made from a whole range of odd things, then PVA isn't exactly inert, just see what happens if you mix it with lead shot! Give it some time to thoroughly dry out, then experiment with some small patches of paint.

[captrees]

I have some ballast that does this. Can't remember the brand because I threw the bag away when I decanted it into a container. Turned it into spilt coal instead.




The Woodlands Scenic stuff doesn't change colour.

[Bigmet]

What IS your grey ballast? Your bag of little grey chippings can be made from a whole range of odd things, then PVA isn't exactly inert, just see what happens if you mix it with lead shot! Give it some time to thoroughly dry out, then experiment with some small patches of paint.

I'd add to this, that it may be more to do with the PVA used than the chippings. It is always advisable to test a little of the proposed ballast material with the adhesive that is going to be used, and allow it to fully go off, before applying it to the layout. Even high quality model ballast made of real stone, of the right type, can end up coloured inappropriately when some cheapo PVA is added to it. (The 'cheapo' PVA may actually be sold at a very high price, the 'cheapo' aspect being in the care taken at production, failing to deliver a pH neutral result.)

[lenht1951]

Well after several days of experimentation I have come to the conclusion that most granite products, Javis, Attwood Aggregates etc etc all react to PVA and darken considerably.
I even experimented using a third meths a third water and a third Copydex and got the same result.
The only product which did not darken was Woodland Scenics, which I believe is made from tree nut by products, so that's the route I will be going down on the main linesmand using a mix of Woodland Scenics and others on the Goods yard and MPDs. Thanks for the input guys

[gppsoftware]

Be aware that not all model ballast is real stone. Some manufacturer's 'ballast' is actually crushed nut shells and it is this type which is often affected by PVA unless the nut shells have been properly treated.

Real stone may well darken as it does absorb moisture.

Probably best to use stone which is properly designed for models as it will be of chosen types to prevent discolouration.

[fourtytwo]

Might I suggest one other thing and that is increasing the dilution of the glue drastically. After trials I have just completed most ballasting at 10 parts WATER to 1 part pva with a few drops of washing up liquid. I still get some darkening of granite chips but not excessive IMOP.

Different dilutions after drying

The ballast was from eazi products who I dont think are in business any more, if they are it is "Granite Ex Fine".