How To Make Furnace Filter Trees

I was changing a furnace filter the other day. Because I had bought a 3-pack of 16 x 25 filters I thought to myself "why not try making some furnace filter trees?" I've read about it often enough, but never tried this technique. 

I had bought a sheet of the green filter that you cut to size, but I wondered how many trees I would get out of a single white furnace filter.

I used wooden bamboo barbeque skewers for the trunks. The ones I had (that we also use for uncoupling cars) were about 12 inches long. I cut them randomly in half to get tree trunks of different heights. I used an X-Acto knife to carve the tip at the blunt cut end. I tried using a handheld pencil sharpener. It didn't work very well. The wood seemed to be too hard.

I also used my Dremel to drill a small hole in the trunk end. After inserting a straight pin I cut off the knob end of the pin and spot glued the pin into the trunk using ACC glue. This provided a means to hold the tree trunk in a block of styrofoam once the foliage was on it.

Step 1

First step in shaping a furnace filter tree
furnace filter tree

I used scissors to roughly cut out circles of the furnace filter material about 1 to 2 inches round. 

I started by slipping the larger pieces onto the bamboo skewer adding layers in smaller sizes until I reached the top of the tree.

Then I used scissors to snip the tree branches so that the branches tapered towards the top. I didn't want the branches to be too uniform.

Closeup of the furnace filter branches
furnace filter tree branches

I probably should have tapered the tree more. Here is a closeup of the weave in the furnace filter material.

The trees are representative of Christmas-type evergreens. The height and width of the trees depend on the scale you're modelling in. I kept these trees between about 4 and 8 inches. It's not critical. You want to mix them up when you plant them on your layout.

Step 2

Trees sprayed with flat black paint
sprayed furnace filter tree

Spray paint the trees black. It's best to do this outside. I stuck them into the top of a cardboard box on the grass for spraying. Spray down wind! Also, it's a good idea to wear gloves.

Use any flat black paint. Spray up from the bottom and down from the top while turning the tree in your hand. Then plant it to dry in the top of the box or a piece of styrofoam.

Step 3

Tree sprinkled with blended turf
final furnace filter tree

Spray the trees with cheap hair spray and sprinkle on ground foam while the branches are wet and sticky. I Used Woodland Scenics blended turf. I sprinkled on the foam over a plastic top from a tree kit so I could recapture spilt foam. It took several applications of hair spray and foam. It's necessary to sprinkle from the bottom as well as the top and sides. 

  • The black paint acts as shadows.

I had pre-stained some trunks with Hunterline wood stain. I don't think I'd bother in future because the paint covers the stain. I will probably spend more time shaping the tree in future. These first attempts can act as fillers on the mountainside. The whole technique is very forgiving and it doesn't take very long to make a bunch of evergreens. I made more than a dozen trees from one furnace filter. That makes the trees pretty inexpensive.

Return from "furnace-filter" trees to the trees overview.

Learn about building terrain.

Methods for modelling roads and streets.

Paint a scenery backdrop.

Catch attention with mini-scenes.

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