Ballast

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lenht1951
Posts: 107
Joined: Wed Dec 19, 2012 7:25 pm
Location: Near Taunton

Ballast

Postby lenht1951 » Tue Mar 16, 2021 10:49 pm

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

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Bufferstop
Posts: 13484
Joined: Thu Mar 11, 2010 12:06 pm
Location: Bottom end of N. Warks line

Re: Ballast

Postby Bufferstop » Tue Mar 16, 2021 11:15 pm

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.
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captrees
Posts: 152
Joined: Fri May 25, 2018 7:45 pm
Location: Kalamunda WA.

Re: Ballast

Postby captrees » Wed Mar 17, 2021 4:40 am

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.

Image


The Woodlands Scenic stuff doesn't change colour.

Bigmet
Posts: 9117
Joined: Tue Aug 14, 2007 2:19 pm

Re: Ballast

Postby Bigmet » Wed Mar 17, 2021 10:27 am

Bufferstop wrote: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
Posts: 107
Joined: Wed Dec 19, 2012 7:25 pm
Location: Near Taunton

Re: Ballast

Postby lenht1951 » Fri Mar 19, 2021 11:26 pm

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 :D

gppsoftware
Posts: 306
Joined: Thu Mar 09, 2006 5:34 am

Re: Ballast

Postby gppsoftware » Fri Oct 22, 2021 1:19 am

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.

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fourtytwo
Posts: 153
Joined: Mon Oct 31, 2016 7:41 pm
Location: Norfolk (Bodecia's country) UK

Re: Ballast

Postby fourtytwo » Fri Oct 22, 2021 12:38 pm

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.
as_dried2.JPG
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".
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