Did you know you can get pre-shrunk foam now so that you don't have shrinkage. I had to let mine foam sit for months when I built my layout because at the time pre-shrunk wasn't available.
Evidently I live under a rock, as I've never heard of pre-shrunk foam. You wouldn't mind explaining it to me, would you?
Thanks,
Mike
My You Tube
Of course you can leave the foam outside in under 60 degree temps - The 'shrink' happens as the air pockets collapse in the foam(at least from what I have been told).
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
jrbernier Of course you can leave the foam outside in under 60 degree temps - The 'shrink' happens as the air pockets collapse in the foam(at least from what I have been told). Jim
In my experience, those air pockets swell right back up later, when the temperature goes up.
The foam can change dimensions because of changes in ambient temperature. Pretty much forever. I noted the phenomenom when the coating I put on over the foam developed cracks long after it had dried/set. Co-incident with termperature rises.
The shrinkage-only would be a separate thing. I've seen that, and it never puffs back up.
Aging for six months has been represented as a cure for the latter problem. I do suspect that the six month term was not scientifically determined. Consider: someone has to store the foam at least six months, measure it "frequently" to determine the cut-off time, and do the measurements under temperature controlled conditions.
Anyone done that?????
Ed
https://foursevenfive.com/foam-fails-reason-5-excessive-shrinkage/
CG
That article cites a 2% shrinkage which is almost 2" over a 8' span. Ken Patterson showed shrinkage on his layout, but it looked like it was more like 1/8"
Our application is different than sticking up in a barn roof, but nobody would be using it for layouts if they were getting 2" gaps.
My Home Depot doesn't mention pre-shrunk. Where are you finding this product?
Henry
COB Potomac & Northern
Shenandoah Valley
CentralGulf https://foursevenfive.com/foam-fails-reason-5-excessive-shrinkage/ CG
rrebell Did you know you can get pre-shrunk foam now so that you don't have shrinkage.
Did you know you can get pre-shrunk foam now so that you don't have shrinkage.
Nope.
Please tell us more.
Don't know how they pre shrink, it could be just from storing but more likely some other method, haven't resurched that as it is ussually not a local big box store item, yet.
rrebell Don't know how they pre shrink, it could be just from storing but more likely some other method, haven't resurched that as it is ussually not a local big box store item, yet.
So, how did you find out about this stuff? Where have you seen it? Was there something on the packaging that said it was pre-shrunk? Was there some particular brand or something?
I had my 2" foam sitting around about 6 months before I was ready for it and I noted that it had developed a wavy pattern with ridges about 2" wide along the 8 foot length. No ridges across the 4' width. However, i also had some 3/4" foam sitting with it remained smooth and it did not develop the ridges. As a result, I am laying the 3/4" foam (smooth) on top of the 2" foam (wavy) to ensure I have a flat surface to lay my Kato Unitrack on. Appears the thicker foam is more susceptable to developing irregularities that may be related to how it is extruded at factory. In hindsight, I think building up with thinner sheets might be prefered over a single thick sheet.
Paul D
N scale Washita and Santa Fe RailroadSouthern Oklahoma circa late 70's
7j43k rrebell Don't know how they pre shrink, it could be just from storing but more likely some other method, haven't resurched that as it is ussually not a local big box store item, yet. So, how did you find out about this stuff? Where have you seen it? Was there something on the packaging that said it was pre-shrunk? Was there some particular brand or something? Ed
PED I had my 2" foam sitting around about 6 months before I was ready for it and I noted that it had developed a wavy pattern with ridges about 2" wide along the 8 foot length. No ridges across the 4' width. However, i also had some 3/4" foam sitting with it remained smooth and it did not develop the ridges. As a result, I am laying the 3/4" foam (smooth) on top of the 2" foam (wavy) to ensure I have a flat surface to lay my Kato Unitrack on. Appears the thicker foam is more susceptable to developing irregularities that may be related to how it is extruded at factory. In hindsight, I think building up with thinner sheets might be prefered over a single thick sheet.