How best to cover rigid foamboard & expantable foam on an incline

[videobruce]

I have a long area that consists of 1/2" rigid foamboard smooth & 'shaved' with expandable foam (also shaved down) on an incline that I'm not sure how to treat.

Go over it with hydrocal or brush full strength PVA glue and sprinkle with medium Talus.


See the photos. (The 2nd pic, note the much darker 'gray' when I painted the expandable foam)

[Pomperaugrr]

I would suggest applying a layer of "Lightweight Spackling Compound" to smooth out the area and add any contour you want. It is extremely easy to work with and very inexpensive. After that dries, I would then apply a coat of earth colored paint, then the PVA brushed on, with a layer of talus sprinkled on. Once that is set, apply another layer of talus and shape/arrange it until you get the look you like. Then soak it all with a 50/50 mixture of matte medium and let set. After that, apply some weeds and and vegetation to show the passage of time since the grading was done.  Take your time and do it step by step. You won't be disappointed.

[videobruce]

As opposed to 'painting' it with PVA then spreading the talus?

[Pomperaugrr]

As opposed to 'painting' it with PVA then spreading the talus?

It is a matter of preference.  I give all terrain a base coat of earth colored latex or acrylic paint, even if it is going to be covered over and not seen.  It is just insurance for me, in case ground cover is thin in places, so I don't see any stark white spackle or blue foam showing through.

There is no one "right way" to do scenery.  Everyone has their own techniques and methods.

[videobruce]

Understood.
Have you encountered any 'adhesive' or lack of issue after you paint the base level of scenery?

[Pomperaugrr]

Understood.
Have you encountered any 'adhesive' or lack of issue after you paint the base level of scenery?

I have never had a problem with adhering later scenery elements to the painted surface.  Sometimes when painting on earth colored paints, I will even sprinkle on a little fine ground foam to add some surface color and texture, especially if I am not going back to do detailed scenery on that area until later on.  I have had good luck using cheap latex paint and even craft paints.  It is an extra step and may be unnecessary, but it seems to work for me.

[wazzou]

I have at times used the yellow mesh drywall tape to hold Sculptamold on slopes where I thought otherwise it would just slough off.

[videobruce]

Is there any issue of hydrocal NOT sticking to foam board and/or expandable foam even after either was 'scraped' to a rough texture?

[MK]

No.  Rough texture makes it even more secure.

[nkalanaga]

If it's on the edge of the layout one of the above suggestions is probably best.

If it's in the middle of a scene, with "flat" ground below the slope, I'd just pile the talus in place and soak it with glue, similar to ballast.  That way you know you have a natural slope, and with enough glue, it isn't going anywhere.

[videobruce]

Thanks all for the input.

[davefoxx]

I would suggest applying a layer of "Lightweight Spackling Compound" to smooth out the area and add any contour you want. It is extremely easy to work with and very inexpensive. After that dries, I would then apply a coat of earth colored paint, then the PVA brushed on, with a layer of talus sprinkled on. Once that is set, apply another layer of talus and shape/arrange it until you get the look you like. Then soak it all with a 50/50 mixture of matte medium and let set. After that, apply some weeds and and vegetation to show the passage of time since the grading was done.  Take your time and do it step by step. You won't be disappointed.

You got my [up]vote.

DFF

[videobruce]

See these pics of the new area that I am tackling. This was done with outdated Sculptamold that turned out looking like cottage cheese. The 'rocks' were too 3D for the size of the area. The area towards the bottom is rigid foamboard filled in with expanding foam that pushed out the foamboard at the base when it expanded.

[BuddyBorders]

Back in the day, we used to use pearelited gypsum plaster, AKA Structo-Lite. It's brown coat plaster for doing plaster walls. Pretty much will stick to anything. We would paint it on with an old paint brush and it had a bit of a gritty texture that added interest. Even if spread thin, it was still pretty strong. Takes paint well for the basic color coat and you can easily add rock castings to it as well. It can be found in the Big Box stores.

Regards,
Buddy

[wvgca]

 there are many ways to accomplish what you want to do, but if using white glue or paint you might want to add some liquid soap into the mix to reduce 'beading' on the finished surface