What's sliming my ballast?

[Ed Kapuscinski]

This isn't the first time I've seen this, but now it's on a part of the layout that matters, so I want to figure out what's going on.

Anyone have any idea what's creating the green "slime" in my ballast here?

I'm using a sanded grout blend, wetting it with water, then applying the standard glue, water and soap mix.

I'm thinking it's some sort of chemical reaction between the rail and something, but I'm not sure what. Any of you crinkly brains have an idea?

[Dave V]

What do you use to soak the ballast before bonding?

[Ed Kapuscinski]

What do you use to soak the ballast before bonding?

Wooder

[Dave V]

Without knowing for certain the chemical composition of Chinesium, there's clearly at least a little copper in there that's oxidizing with your "wooder." The rail must not have been thoroughly alloyed.

[Scottl]

Yeah, metal oxidation, probably copper.  Nickel-silver alloy likely has other metals in it too due to impurities and manufacturing tolerances.  Could be the mortar in the grout whis is not chemically neutral (likely alkaline with carbonate) causing a reaction and retaining some water even when dry.

[Ed Kapuscinski]

Yeah, metal oxidation, probably copper.  Nickel-silver alloy likely has other metals in it too due to impurities and manufacturing tolerances.  Could be the mortar in the grout whis is not chemically neutral (likely alkaline with carbonate) causing a reaction and retaining some water even when dry.

That's what I was thinking, and also afraid of.

Now to think about how to combat it.

[Dave V]

That's what I was thinking, and also afraid of.

Now to think about how to combat it.

If the grout's involved, you could confirm or rule it out by doing a test piece with Woodland Scenics or Scenic Express ballast...something purpose-made for your application. If that turned green on ya, well...then I'm out of ideas.

[peteski]

Nickel-silver is a brass alloy, so all  nickel-silver contains copper. That's just given.  Why it is reacting to plain water?

That looks like weathered rail. The weathering solution is acid-based, so maybe  the rail did not get completely rinsed or the not neutralized,  so when some of the acid gets reactivated by water, it reacts with the nickel-silver?  How's that for some Polish Logic?   

[C855B]

Concur - turquoise green = Cu(OH)₂, although there are other copper salts that exhibit a similar color. That's just the most common.

... Could be the mortar in the grout whis is not chemically neutral (likely alkaline with carbonate) causing a reaction and retaining some water even when dry.

Yeah, that could easily be the source of the reaction. It's not like ground rock or walnut shells are going to be 7.0 or anything close, but the pH of portland cement is quite high (12.0-13.8 ) and you may have done it to yourself. If it were me, I'd spend a few pennies and order pH strips off of eBay (or whatever), and see where you stand.

I've had to deal with similar issues. A few years ago I noticed that some sections were needing constant cleaning, and the web and base were "naturally" weathering. The distribution of the problem - locations that were "spot tacked" - seemed to hint at an association with the glue. Turns out the "better", more water-resistant carpenter's glues (Titebond II and III) appear to do something similar to your situation. Later sections where I "downgraded" to Titebond Original don't exhibit this problem.

[Dave V]

Nickel-silver is a brass alloy, so all  nickel-silver contains copper. That's just given.  Why it is reacting to plain water?

That looks like weathered rail. The weathering solution is acid-based, so maybe  the rail did not get completely rinsed or the not neutralized,  so when some of the acid gets reactivated by water, it reacts with the nickel-silver?  How's that for some Polish Logic?   

Unless Atlas now makes pre-weathered rail now, I don't think that's it. Ed showed how he paints his Atlas track...those are acrylic browns. So maybe...the paint?

[peteski]

Unless Atlas now makes pre-weathered rail now, I don't think that's it. Ed showed how he paints his Atlas track...those are acrylic browns. So maybe...the paint?

Ok, I thought it was ME C55 track.  In that case yes, it might be the acrylic paint, or like Mike mentioned, the pH of the grout.

[Ed Kapuscinski]

Ok, I thought it was ME C55 track.  In that case yes, it might be the acrylic paint, or like Mike mentioned, the pH of the grout.

I think we're onto something with the pH of the grout. How would I go about getting the pH of the stuff? I can't exactly dip a strip into it like a liquid, can I?

[Dave V]

I think we're onto something with the pH of the grout. How would I go about getting the pH of the stuff? I can't exactly dip a strip into it like a liquid, can I?

Lick it. Like lick it a LOT. Then shove it down your pants and wait 10 minutes. Then lick it again.

[C855B]

I think we're onto something with the pH of the grout. How would I go about getting the pH of the stuff? I can't exactly dip a strip into it like a liquid, can I?

Just make it wet enough for the test strip. It may not be the most accurate method, but I think it'll be close enough.

[Ed Kapuscinski]

Just make it wet enough for the test strip. It may not be the most accurate method, but I think it'll be close enough.

Cool. Thanks!