Chalking DTFB: an old technique on a new material.

I was thinking the other day about DTFB and it's unique paper, compared to the more expensive foam boards out there. I was trying to come up with a good way to add a low weight colored finish to my FT Mini Scout currently in progress.

The aha moment struck quickly. "This paper is a bit like tissue, isn't it," I thought."I could probably chalk it just like a stick and tissue model, couldn't I." And so I attempted to do just that, but not without a test of the materials on some scrap first.

For those of you not familiar with chalking tissue, there are a number of good tutorials out there on scratch built freeflight websites, but here's a brief overview.

Materials needed:

Artist's pastel sticks (not oil based or watercolor sticks)

Sand paper 150 grit or so, something to make small dust particles

Tissue paper (DTFB in this case)

Applicator (tissues, toilet paper, or paper towel) I found paper towel to work best without tearing itself up.

Krylon satin clear

Step 1) Take your pastel stick and sand a bunch of it into dust.

Step 2) Wipe up some of the dust with your applicator.

Step 3) Work the dust into the paper with steady presssure on the paper towel. Repeat steps 1-3 as necessary.

Step 4) Mist an even coat of Krylon satin clear over everything to seal it. Gloss and flat clearcoats probably all work, but the satin clear dries in under ten minutes. I usually do two light dustings, this also helps add moisture resistance to your model.

Note: I did not say waterproof. I ran one of my samples under the tap for a few seconds to see what would happen. Now, the water didn't bead off, but neither did it soak in. I know tissue covered models can still absorb some moisture even with the coating. On the plus side, clear krylon doesn't warp DTFB like WBPU (Water Based Polyurethane) can.

I cut three test strips and weighed each, they all weighed in at about 4 grams. One was left unchalked, the second had an application of yellow and peach on one side, the third had yellow and brown on one side and plain yellow on the other. Both colored samples were then sprayed with sealer on both sides as outlined below and re-weighed. The sample with only one side coated still showed 4g. The sample coated on both sides just tipped the scale to 5g, wavering between 4g and 5g. So it's rather clear that this technique adds minimal weight. There are, however, limitations. I didn't think to attempt this until after my Scout was built, so when I went over everything with my linen color (peach andyellow) anywere non-porous (hot glue, tape) would not take color. I would recommend chalking everything pre-assembly to avoid this.

Also I would like to mention, I have not tried this on higher end poster board and foam core but imagine their smoother surfaces would not take color well, if at all. For coloring and sealing planes where weight is a concern, and you don't want extremely saturated color I would definitely consider the chalking method. If you're looking for bright, vivid colors that really pop, or are building something like a seaplane that needs to be waterproof I would suggest sticking with WBPU and other methods.