Ground foam discoloration HELP

Well, that's different.   I have used Woodland Scenic ground foam with white glue / water mix and not had this problem.   Maybe you got a bad batch of the stuff.

Steve

Where did you source your water from? What contents were in the container you used prior to mixing (or spraying) the glue and water? I wouldn't be at all surprised to learn that bleach would discolor foam.

If you mean the darkening that occurs when one area is wetted next to an adjacent dry area, that is normal.

If you must flood an area, do it uniformly  without dry spots.

Better yet, be more sparing with the diluted glue over an area that has some foam down already.

My technique:

1. Paint the plywood/homosote dark brown.

2. Apply diluted glue/matte medium with a paintbrush.

3. Sift fine foam over the glue until no wetting shows through. This will avoid darker wet spots. Vacuum excess when dry.

4. When dry, use thicker glue to add coarser foam or clump foliage. I use full strength white glue for the clump foliage and extra coarse foam. This way moisture will not wick into dry areas.

This is one reason why I ballast before adding ground foam along the sides of the track. Ballasting requires really soaking an area which might cause discoloration where the ballast glue seeps into surrounding scenic foam. Adding foam after ballast glue is dry avoids this.

Jim

Thanks for all the comments gentlemen.  I think I may have found the problem.  I have a can with assorted reclaimed ground foam that I used on this diorama.  I think there may be some Plastruct ground foam mixed in the container.  When I add the alcohol and then glue mixture, the green turns fluorescent. Looks really bad and hard to see in the photo.  I think the plastruct product is causing the problem.  I going to do a test board and find out.  I'll let you know.  Thanks again for the help.

@rattler21 posted:

What is the intended purpose of the alcohol?  John

You can add a tiny bit of alcohol to a glue/water mix as a wetting agent, it makes it soak in quicker. If the poster used too much alcohol that might have affected the dye on the ground foam, you literally use a drop or two in a typical batch. 

Alcohol is a great wetting agent for ballast, but it is unpredictable with many scenery material dyes (as you found out).

Usually, ballast is soaked with either alcohol or "wet" water with a few drops of dish soap. Then, dilute glue is applied also with a few drops of dish soap as a wetting agent.

With other scenic materials such as ground foam, I do not recommend using alcohol nor should you wet down the area first before adding dilute glue. See my first post above for a better method.

Jim

Thanks for all the comments and help.  I think I found the culprit.  As I suspected it was the Plastruct foam that was changing color.  I did a test board.  The first square is plastruct foam only.  The last square is a mix of plastruct and woodland.  The two center squares are both woodland only.

I used plain water, plain glue, distilled water, alcohol first then diluted glue, wet water (soap) and diluted glue with a drop of alcohol mixed.  The plastruct discolored with every application.  The woodland only got a little darker, which is expected and not an issue. The color change is not as apparent in the attached photo as it is in person.

Thanks again. The plastruct went in the trash! It was very old and may have deteriorated over the years.