My ballast is turning into Peanut Brittle!

I have had no similar problems.  I use the wet water but with a 50/50 mixture of white glue and water. 

I'm not certain, but I wouldn't be surprised if dry white glue was more plastic (i.e., flexible) than matte medium. Most matte medium is acrylic, and is formulated to dry to a hard, protective surface. White glue dries to a soft, somewhat flexible texture.

So what have you decided to do with the layout and this project? The reason I am asking is I have the same situation you have. My layout is in the garage and breezeway of my house. And I'll be applying ballast in the upcoming months. I hope it turns out good on your decision.    Scot

Is the ballast on the Fast Track? (Will white glue adhere to plastic track?) Have seen many modular layouts where the ballast is coming off in same size or larger chunks than yours right from the plywood and cork, in most cases it seems not enough wet water liquid/glue mixture to get the ballast stuck to the surface was used. The friend who showed us how said if it isn't running, there isn't enough. Plus, once the initial glue mix is dry, any additional coats will not penetrate the initial now hard coating.

Maybe an image of where is is coming loose? As you clearly note, wood is an ever changing platform with temp and humidity!

Mike:

You mentioned Fastrack.  Is Fastrack where the matte medium is failing?  I would expect that the matte medium wouldn't stick to the plastic very well. If not, what is the surface where it's letting go?  It looks like the matte medium is sticking to the ballast pretty well but is not bonded to the substrate.

For my ballast, I used a mix of about 40% matte medium, 40% water and 20% isopropyl alcohol which has been down about 6 years without trouble.  I have Ross/Gargraves over cork roadbed on top of painted Homasote, but fairly stable temperature/humidity.

There is no one particular area.  I've noticed it cracking at the spots where it comes up against the  FasTrack plastic base.  And I've also noticed it cracking in the spaces between the two loops on the base of my layout...where the ballast would be resting directly on the plywood surface.

The drying out and/or cracking of ballast is fairly common. It's happened on a few of my layouts. Generally caused by fluctuations in room temperature and/or not enough bonding agent for the ballast.

If you haven't already removed most of the ballast, you might consider re-wetting the ballast in place, then re-apply the bonding solution (I use the white glue/water combo), maybe press the cracked areas back together, then allow to dry. You may need to re-apply a little ballast here and there.

I would say it could be the environment your layout is in.  We did the same with our Fastrack but we did use Elmers mixed with water and a little alcohol.  No problems with ours yet but it is in a controlled environment too (basement).  Good luck with your issue, hopefully you can restore or redo the areas effected with ease.  Nick  

Looks like not enough bonding agent and/or not enough penetration into the ballast. To make bonded ballast really stick to a plastic roadbase I might give it a brush of latex bonding agent (Concrete bonder) first. You could ballast your truck if you gave it a good coat of latex bonder first. I build for a living and if you like not getting called back it is a good idea to use a latex bonding agent even if you are sure you are going to get a good bond with tile or stucco, etc.

Mike posted:

It's an unheated, non-insulated garage.  My guess is that the wild fluctuations in temperature and humidity....95 and humid one month...single digits a few months later....are causing the ballast (or the underlying plywood) to expand and contract just enough to crack the surface adhesive.

I would completely agree with this assessment.  I believe Leon recommendation is a good one:

If you haven't already removed most of the ballast, you might consider re-wetting the ballast in place, then re-apply the bonding solution.

I have done the above several times in areas where I tear up the track and insert a new switch or line.  I would also use Elmer's glue with water and not the commercial product.

I always used to apply wet water on/in the dry ballast until its running out on each side[ I did the same if using matte medium in place of Elmers]. Then I apply the mixture of 50% white glue and 50% wet water until its running out each side. Messy and uses a lot of paper towels but on a '97-built layout that I recently dismantled the ballast was hard and secure after 12 years. [place a tarp under the layout when doing this messy application].

I wanted to save a couple of hi-speed crossovers so I applied boiling water planning to clean the loosened ballast off the turnouts. The result was breaking the cork, turnouts and ballast loose from the foam underlayment as a unit but there was no breakup of the ballast itself. As a result I decided to reuse the crossovers and ballast on my attic layout as a unit---the old cork, ballast and Ross turnouts. The old blended right in with the new [Brennan's] ballast.

I think that is the secret.  I did that too - hard to see it seeping out the bottom edge.

This sort of conundrum is one of the reasons why I prefer to use gravity, alone, to hold track ballast in place.  Here in Meeshigan we're not so prone to having the earth move suddenly and violently on occasion.  I don't live next to the CN or CSX mainline having a lot of traffic featuring wheels with flat spots passing by.  Heavy truck traffic is not at all common on our street.  We're not aligned with the runway of our regional airport.  Military maneuvers featuring swarms of choppers bringing in the defending company are...so far...unknown to us.  And, best of all, no one is starting construction of a bridge or skyscraper next door for which the pile-drivers are seeking bedrock. 

And the 25'X40' layout is not intended nor designed to periodically change its attitude by 90 degrees for storage purposes.

Ergo, as with the real railroads, I think I'll not pour goop all over it.  Gravity works well.  Besides, if I want to change some track routing, repair/replace a piece of trackwork, do some electrical work on the rails, etc., etc., I'll just put a clean filter bag in the Dust-Buster, vacuum up the loose ballast, do the track work, replace, tamp, groom the ballast again with a soft brush. 

But, that's just my paradigm. 

Oh, I also avoid synthetic, static-charged ballast products.  .....and Mexican Jumping Ballast.

TEHO, of course.

KD