Wednesday, March 14, 2018

New England Foam Forestry

This Modelers New England Dilemma

Modeling New England means modeling many trees, specially on a branchline like New Haven's Berkshire Line in western Connecticut and Massachusetts. My dilemma is fabricating trees, what could eventually amount to a thousand trees or more.  Although building rolling stock, structures and vehicles is something that I totally enjoy, fabricating trees is not!

Scenic Express SuperTrees make nice small foreground trees and I will continue to use them where I think they will make the best presentation, but with the amount of them that would be required for the background foliage on this layout they are not financially nor timewise practicable.

Foam Forest

Initially when planning this layout I thought making "puff ball" trees would be the easiest way to blanket the background with the amount of trees required to represent the part of New England being modeled. I tried making a few puff balls but it quickly became clear that this method was not something I was willing to do on the entire layout and a new plan was needed.

The following method is the way I decided to fabricate the blanket tree canopy for this layout. Although this method takes a few days to complete because of drying time between steps, the actually fabrication time spent is minimal. Great Stuff, an expandable foam dispensed from a 16 oz spray can, will form the tree canopy shapes. These foam shapes will then be covered with black poly fiberfill and finished with various colors and textures of scenic flocking materials.

I decided to make the foam tree canopies as separate sections that would be formed on the layout then finished with the scenic materials on the workbench before installing the sections on the layout. The section that is the subject of this post is about 7' in length, about the maximum length that will fit my workbenches. I find that the finished sections are easily blended together after installation on the layout.

Wax paper covers the layout area below where the foam will be sprayed. When cured the foam will retain the shape of the terrain that it was sprayed over making the section easy to install when finished. The foam will not stick to the wax paper.

An initial coat of foam has be sprayed over the wax paper below, after a few minutes packing peanuts were attached to the still very tacky foam. The peanuts are just a filler and were used because they were on hand, this filler most likely could been anything from news paper to leftover pieces of extruded foam board. If the foam is too thick it will take a long time to fully cure and is a waste of material.

A second coat was then sprayed over the peanuts. Dispensing short spray bursts of foam from the can leaving behind irregular and random shapes, nooks and crannies are best. 

As a side note, the reason that a peanut filler was required when making the section above is that the landform terrain was already glued in place on the layout because puff ball trees had been planned on being installed. Going forward with the remainder of the layout extruded foam board as below will be shaped to the near the full height of the tree line so only a thin coat of spray foam will be needed.

After curing overnight this is the fully cured foam section being checked for fit. Parts of the section that look undesirable will be broken off at this point.

When I was satisfied with the shaping of the section it was taken outside and painted with black enamel from a spray can.

After the paint was dried a mixture of 1 part Matte medium and two parts water was sprayed over the foam section, then layers of stretched out black poly fiberfill were placed over the foam and worked into the contours. An overspray coat of the matte medium mixture was then sprayed onto the poly fiberfill and let to dry overnight.

This is how the section looks after the poly fiberfill has been affixed to the foam. One last test fit on the layout.

The poly fiberfill is very stiff after the matte medium mixture has cured, the fiberfill is pushed down into the contours then another coat of matte medium is sprayed over the section in preparation for the scenic materials.

Several varied colors of scenic materials have been dispensed over the wet matte medium below.

When the scenic materials have achieved a look that I like the entire section was oversprayed one more time with the matte medium mixture and let dry overnight on the bench.

This is the finished tree section on the layout. A few dabs of adhesive caulk hold the section in place, double sided tape could also be used.

This is a fast and inexpensive method for me to make the background foliage for the layout. This section took about 3 hours of actual working time, the can of foam was $4.25 and the spray paint was $1 both from Home Depot. I prefer to do the spray painting outside and the application of the scenic materials over a tarp on a workbench inside or out, but could be built in place on the layout if the painting step used a non solvent type paint.

The tree section can easily be removed to have additional scenic materials added or tweaked in place if desired. The section is light weight but rugged and not subject to damage. I may add some random or groupings of conifer tree tops where appropriate on future sections.

Works for me!


  1. This is brilliant. Thanks again!

    1. Thanks Fred, I don't know about brilliant, but it's at least different! Joe