Colorado Midland Railway Engineering Report

[CRL]

   The bubbles in the water are from using foam under it. Foam out-gasses and always will. I learned my lesson and now lay down this 1/8" hard board for a water base.

Couldn’t you seal the foam base of your riverbed with a latex paint designed as a vapor shield?

[Dave V]

Couldn’t you seal the foam base of your riverbed with a latex paint designed as a vapor shield?

I've noticed this phenomenon on the RGS as well even after sealing the riverbed with both plaster and latex paint.  You can't fight the chemistry and the physics...the gas has to go somewhere.

[Chris333]

Couldn’t you seal the foam base of your riverbed with a latex paint designed as a vapor shield?

I sealed mine with paint and sceniced the bottom of the creek with glue/matte medium. Still got bubbles.

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Right around the 1:15 mark.

The river base on my HCD Erie layout is the wood door itself, no bubbles.

[nuno81291]

Not to hijack the thread but I have lately been using Masonite as my water bases.. haven’t seen any out gassing effects yet. Have experienced it with my foam efforts. 

[CRL]

I was not referring to regular latex paint. I was asking about some of the specialized sealing products specifically designed to block outgassing from wallboards for people sensitive to the VOC’s contained in these products.

[Dave V]

I was not referring to regular latex paint. I was asking about some of the specialized sealing products specifically designed to block outgassing from wallboards for people sensitive to the VOC’s contained in these products.

Wouldn't know without trying, but maybe.

[Chris333]

Wouldn't know without trying

And then waiting a year to see what happens...

[CRL]

Styrofoam also shrinks some, so also possible this shrinkage contributed to the bubble issue.

[Dave V]

Styrofoam also shrinks some, so also possible this shrinkage contributed to the bubble issue.

Nah, we're talking bubbles like on pizza crust.  That's clearly from outgassing.  Shrinkage would cause buckling and wrinkles, no?

[CRL]

That’s pretty dramatic. I’ve seen pinholes develop in a finish over a composite panel if the finish was applied after the panel started heating up before the finish cured. But I’ve not seen this happen after the finish coating cured.

[peteski]

Nah, we're talking bubbles like on pizza crust.  That's clearly from outgassing.  Shrinkage would cause buckling and wrinkles, no?

That doesn't sound like just air bubbles - more like delamination of the resin.  Not sure if outgassing would result in bubbles like those. Maybe there is some chemical reaction going on between the resin and paint/sealer?

[Dave V]

That doesn't sound like just air bubbles - more like delamination of the resin.  Not sure if outgassing would result in bubbles like those. Maybe there is some chemical reaction going on between the resin and paint/sealer?

I don't know...  I do know it's happened both on the Midland and on the RGS built here at 6,800 feet and typically our station pressure is about 78-80% of what it is down your way near sea level.  So maybe the outgassing is enhanced by the pressure differential?  I simply use latex paint and Hydrocal to seal the riverbed...although I tend to put "stuff" on the riverbed like rocks and other debris, glued in place using glue diluted with alcohol.  Might that play a role?

[Chris333]

I got a bunch of bubbles around 1/8" dia. Popped a few and there was a little dimple left over. Happened with this layout:
https://photos.app.goo.gl/ppTAPox8WDB1t2Pp7

So now the new layout has wood under all the water:
https://photos.app.goo.gl/nCo3XARxuH2tSvjr9
https://photos.app.goo.gl/6oCtpWh2CKkXhPWPA
https://photos.app.goo.gl/xFvYgLRSnR4M8maC6


The bubbles could have been popped and filled back in, but it would be on-going.

[Dave V]

All the woulda coulda shoulda doesn't help the damage that's done...so all I'm really able to do is cut the bubble out and refill the hole with gloss medium.  It helps.  It's not perfect, but for moving water it's okay enough.

[Chris333]

And the bubbles are the sort of thing that I doubt would even show in a photo. Well maybe if it was something like a flat lake.