Colour change .

I bought some new ballast thinking it would be a close enough match to that already laid. It was looking ok until I applied the IPA/water mix and as expected the ballast colour darkened as it was wetted.Now some 5 days later and the ballast colour has hardly lightened much at all ?. It appears to be dry and has firmed up as expected. I tried a hot air gun on it but it's made no difference 🤔.  I'm interested to hear if anyone knows what's caused the ballast to dry a different colour ?. 
I'm also interested to hear your thoughts on the two colours, which one is more realistic.

[user=559]johnmay[/user] wrote:

I bought some new ballast thinking it would be a close enough match to that already laid. It was looking ok until I applied the IPA/water mix and as expected the ballast colour darkened as it was wetted.Now some 5 days later and the ballast colour has hardly lightened much at all ?. It appears to be dry and has firmed up as expected. I tried a hot air gun on it but it's made no difference 🤔.  I'm interested to hear if anyone knows what's caused the ballast to dry a different colour ?. 
I'm also interested to hear your thoughts on the two colours, which one is more realistic.

John.

That new ballast you got looks quite dark to me ?
Some granite & perhaps other stone based ballasts change colour to a greenish tinge when they come in contact with Pva.
I have always used Woodland Scenics ballast which I believe is not stone based & retains its colour better under contact with pva.
Some modellers also use a pva glue mix which is far too strong for what's needed especially for layouts which are not shown at exhibitions.

Tony.

Hi Tonythanks for your comments. I may try woodland ballast as I feel the ballast I have is just too dark.
Your comment re Pva being too strong for non exhibition ballasting is interesting. What do you use to fix ballast ?.

If the supplier has two grey shades, it's possible one of your batches was supplied in error. Original invoices would tell you what you thought you were getting and if they're wrong then you've got grounds for complaint.

Your tub they're in appears to be marked "Dark Grey…" and the original does not look dark enough to fit that bill. Some back checking is in order here to sort out where.things have gone wrong.

 
If it is a stone based ballast there is the possibility of reaction between acetic acid in the glue and minerals in the stone. Not doubt that's a possibility but is a secondary issue. The fresh ballast clearly is totally different. first check you got what you thought you were getting.

Colin

Hi John,

Looks OK to me. New light grey ballast meeting old grey. Very prototypical.

Nigel

Agreed with Nigel - I wouldn't sweat it. That kind of mismatch happens with ballast in real life.

[user=2170]Colin W[/user] wrote:

If the supplier has two grey shades, it's possible one of your batches was supplied in error. Original invoices would tell you what you thought you were getting and if they're wrong then you've got grounds for complaint.

Your tub they're in appears to be marked "Dark Grey…" and the original does not look dark enough to fit that bill. Some back checking is in order here to sort out where.things have gone wrong.

 
If it is a stone based ballast there is the possibility of reaction between acetic acid in the glue and minerals in the stone. Not doubt that's a possibility but is a secondary issue. The fresh ballast clearly is totally different. first check you got what you thought you were getting.

Colin

Hi ColinI was supplied the colour I asked for bud. The writing on the tub is mine. When dry the ballast is the colour I want, it's only an issue once it's been wetted with the IPA/water mix , then as expected it's darker when wet but it stays dark when dry and set !.
I personally prefer the ballast to be a lighter shade when dry as shown in the older ballasting at the start of the track.
Your observation regarding Acetic acid in the Pva glue mix is interesting. Do you have an alternative suggestion to PVA ?.
Regards John 

[user=1632]BCDR[/user] wrote:

Hi John,

Looks OK to me. New light grey ballast meeting old grey. Very prototypical.

Nigel

Hi NigelI get your point re prototypical,it's a personal thing I guess but I prefer the ballast to be a bit lighter than it has become in this case.  Ideally I would like to be able to fix the ballast without changing its colour so dramatically, so any suggestions are welcome bud.
Regards John 

[user=1916]ZeldaTheSwordsman[/user] wrote:

Agreed with Nigel - I wouldn't sweat it. That kind of mismatch happens with ballast in real life.

For sure mismatch is good and can add realism and interest , but it's just a tad too dark for my taste I'm afraid.
Cheers 🍻

[user=559]johnmay[/user] wrote:

Hi Tonythanks for your comments. I may try woodland ballast as I feel the ballast I have is just too dark.
Your comment re Pva being too strong for non exhibition ballasting is interesting. What do you use to fix ballast ?.

Hi John.

I use the following glue mixture.
I part Pva.
2 or 3 parts Water.
2 or 3 parts Methylated Spirits.

I give the ballast a good spray of Meths with a spray bottle.
After this I use a dropper or syringe to lay on the glue mix.
With the Meths mix the glue just runs straight into the ballast.
Wear a mask if in an enclosed space & no smoking or lighted flames.
Leave for 24 hours & clean up any stray bits.

Tony

[user=559]johnmay[/user] wrote:

Hi Colin I was supplied the colour I asked for bud. The writing on the tub is mine. When dry the ballast is the colour I want, it's only an issue once it's been wetted with the IPA/water mix , then as expected it's darker when wet but it stays dark when dry and set !.
I personally prefer the ballast to be a lighter shade when dry as shown in the older ballasting at the start of the track.
Your observation regarding Acetic acid in the Pva glue mix is interesting. Do you have an alternative suggestion to PVA ?.
Regards John 

Sorry,

I misunderstood, from your wording I thought your photo of the tub showed both new and older batches. The right hand side is clearly darker, it seemed improbable that you'd wet it while still in the tub.

  If you were supplied exactly the same colour viewed dry, then I get your point. If not, then my point stands, the supplier might have said they supplied the same shade but it might not have been for whatever reason. The first batch doesn't seem to be a "dark grey" by any reasonable measure.

Not sure if this will help but I downloaded your track photo and extracted image samples to aid comparison,



Top left is the original laid ballast, it has a distinctive green tint (acetic acid + nickel or copper perhaps). Fresh ballast in the tub is to the right and the 2nd laid ballast is below. What was interesting (not shown) was when I adjusted the Gamma for the 2nd sample to 2.3 "times" lighter the shade is clearly grey not green.

 The colour balance of your photo was spot on so it's not that giving the green shade to the 1st Ballast
 

[user=710]amdaley[/user] wrote:

[user=559]johnmay[/user] wrote:

Hi Tonythanks for your comments. I may try woodland ballast as I feel the ballast I have is just too dark.
Your comment re Pva being too strong for non exhibition ballasting is interesting. What do you use to fix ballast ?.

Hi John.

I use the following glue mixture.
I part Pva.
2 or 3 parts Water.
2 or 3 parts Methylated Spirits.

I give the ballast a good spray of Meths with a spray bottle.
After this I use a dropper or syringe to lay on the glue mix.
With the Meths mix the glue just runs straight into the ballast.
Wear a mask if in an enclosed space & no smoking or lighted flames.
Leave for 24 hours & clean up any stray bits.

Tony

Hi Tony, 

Well I've tried a number of different wetting materials now and the upshot is that the ballast immediately turns to the dark colour you see in the photo, and it's doesn't dry to its original colour as has always been the case with any other ballast I've used. So the plan now is to get some from Woodland scenics and see how that goes. I'm not sure if I will leave the dark ballast already laid. Every days a learning day 🤔👍

[user=2170]Colin W[/user] wrote:

[user=559]johnmay[/user] wrote:

Hi Colin I was supplied the colour I asked for bud. The writing on the tub is mine. When dry the ballast is the colour I want, it's only an issue once it's been wetted with the IPA/water mix , then as expected it's darker when wet but it stays dark when dry and set !.
I personally prefer the ballast to be a lighter shade when dry as shown in the older ballasting at the start of the track.
Your observation regarding Acetic acid in the Pva glue mix is interesting. Do you have an alternative suggestion to PVA ?.
Regards John 

Sorry,

I misunderstood, from your wording I thought your photo of the tub showed both new and older batches. The right hand side is clearly darker, it seemed improbable that you'd wet it while still in the tub.

  If you were supplied exactly the same colour viewed dry, then I get your point. If not, then my point stands, the supplier might have said they supplied the same shade but it might not have been for whatever reason. The first batch doesn't seem to be a "dark grey" by any reasonable measure.

Not sure if this will help but I downloaded your track photo and extracted image samples to aid comparison,



Top left is the original laid ballast, it has a distinctive green tint (acetic acid + nickel or copper perhaps). Fresh ballast in the tub is to the right and the 2nd laid ballast is below. What was interesting (not shown) was when I adjusted the Gamma for the 2nd sample to 2.3 "times" lighter the shade is clearly grey not green.

 The colour balance of your photo was spot on so it's not that giving the green shade to the 1st Ballast
   

Hi Colin,   top left is my preferred finished, but having said that I'm quite happy with some variation but not to the degree the new ballast has shown.

I've tried a few wetting mediums but have the same result with each.  Can I ask what you use to set your ballast?.

Hi,

I've no idea what you might use if the acidity in PVA is causing the darkening. This sounds like an issue to address back to the supplier company, you're not their only customer and PVA is the glue of choice to set ballast in place, that's what I'd do if still unhappy.

I had no issue but then I used Woodside Scenics ballast which from others comments is not rock.

Sorry I can't be more help. Good luck

Colin

ColinI have been in touch with the supplier so will wait for a response. Be interesting to have their thoughts.
Cheers 🍻

Hi John,

Cheap PVA from pound stores usually means high acetic acid content (that's why it's cheap). Get the ones that say "neutral". I thought green ballast was an issue due to the use of copper/nickel alloy rails (including N/S). I've used granite for the past 10 years, never had this problem. Granite copper and nickel content is usually very low , so unless the granite had a vein of copper- or nickel-rich mineral running through it (always possible if the granite was cheap stuff from the edge of the pit)…..Or is it tailings from a copper or nickel mine?

You haven't said what mineral your ballast is or who is the supplier. Nice to know so we can avoid it.

Nigel

Just checked the SDS of the PVA glue I use (LePage/Henkel) - pH 4.5. For those who remember their chemistry that's about 0.0001M. To put this in context, distilled white vinegar is about 0.85M. So 8,500 times less. Neutral white glue is available from craft stores. The pH range of neutral PVA glue is usually 4-6. I'll stick with what I have (pun intended).

The right shade of grey paint will easily sort this

Use PLedge/Kleer to stick down the ballast. No greening, little need for 'wet water'and it makes the room smell nice!

[It also dissolves with a little warmish water with a very dilute household ammonia therein.]

Douglas the Smartar%e

[user=1632]BCDR[/user] wrote:

Hi John,

Just checked the SDS of the PVA glue I use (LePage/Henkel) - pH 4.5. For those who remember their chemistry that's about 0.0001M. To put this in context, distilled white vinegar is about 0.85M. So 8,500 times less. Neutral white glue is available from craft stores. The pH range of neutral PVA glue is usually 4-6. I'll stick with what I have (pun intended).

That seemed to be way too low a concentration to give that pH. Physical Chem was not my strength but with Acetic Acid being a weak acid (pKa 4.75) a 1M solution has pH of 2.4. This is why vinegar (5-8%; 0.8-1.3M Acetic Acid) goes OK on chips without searing away your mouth. Likewise with Lemon juice.

By my Calculation 0.01M Acetic Acid has a pH of 4.4 i.e 2 Log units higher than 1M.

Colin

I used 2 different calculators to determine that 0.0001M acetic acid (0.1mM) = pH 4.47 (theoretical, will be dependent on what else is in the mix). Within the specifications of  of "neutral" PVA. Going to 0.001M (1mM) = pH 3.91. Not so good. Pure copper is pretty resistant to acetic acid. Exposure to air forms an oxide layer that reacts with the acetate ions in PVA. I had forgotten what a complicated reaction this is.

Irrespective of the decimal points, go for decent, neutral, PVA to avoid green verdigris. Although concrete sleepers will often have moss growing where water from diesel engine radiators leaks. Check my pictures of Banbury Station.
Nigel