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Building Tips and technical articles. => Building techniques => Topic started by: Tim Wescott on July 17, 2019, 11:00:03 AM
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Coloring epoxy.
So, I have this cockpit that I painted flat black, because the level of detail I was aiming for was to get the general shape, and nothing else.
I'm planning on gluing it on using epoxy mixed with charcoal dust, to get something of the consistency of epoxy+micro-balloons, but dead black.
So -- anyone done that? How'd it work? Is it brilliant, or stupid? I could always use straight clear epoxy, but I'd like something a bit gap filling.
(https://stunthanger.com/smf/scale-models/ercoupe-build-(slow)/?action=dlattach;attach=300758;image)
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Well, it mixes well and certainly makes things black. This is 5-minute epoxy mixed with the charcoal dust from a peanut-sized piece of charcoal (probably fir, although the burn pile it came from had just about everything). There's not enough charcoal in there, but things are looking good in the opaque and black department, and this mixture would certainly be nicely self-leveling, although more shiny than I want.
When I get home from work I'll see how good the adhesion is.
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Guess you answered your own question.
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Guess you answered your own question.
Partially. But if someone's lurking out there thinking "well, when I did it the thing broke after 6 months" -- I want to hear!
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Your reinforcement is burnt wood.
I prefer "manufactured graphite".
If you mix in just a little to color it, it should work just a little less good than straight glue.
Will it? If I fill epoxy with little bubbles of glass or phenolic, it works a lot better for some purposes. I'm thinking that crushed charcoal (er -- manufactured graphite dust) should act somewhat like microballoons, only much blacker.
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I guess you could use crushed pencil lead. Er, graphite, that is.
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I guess you could use crushed pencil lead. Er, graphite, that is.
Most pencil lead is graphite powder with clay mixed in for hardness. I'd be afraid of the result being gray, not black.
Come to think of it, I now want to get some really soft pencils, and try them for marking balsa. I'm really not happy with marking balsa with #2 pencils. I wonder how a really soft one will work.
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I think you can buy quite fine medical carbon powder at pharmacy. At least in 80’s-90’s in Finland.
Then, you can buy graphite powder or very short cut carbon fiber (I have 220 micron/0.22mm) from composite suppliers.
In your case I guess I’d prefer medical carbon or some black powder used for tinting paints, they would give a very fine texture.
But maybe you should use something slower and thinner than 5 minute epoxy, like laminating resin? L
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I think you can buy quite fine medical carbon powder at pharmacy. At least in 80’s-90’s in Finland.
Then, you can buy graphite powder or very short cut carbon fiber (I have 220 micron/0.22mm) from composite suppliers.
In your case I guess I’d prefer medical carbon or some black powder used for tinting paints, they would give a very fine texture.
But maybe you should use something slower and thinner than 5 minute epoxy, like laminating resin? L
The short carbon fiber would be just the thing if I felt that strength was an issue -- I'll keep that in mind.
I'm planning on using something slower for the real thing -- the 5 minute epoxy was just to put some "quick" into a quick test.
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West Systems sells graphite as an additive for their epoxy system. Part 423, you can buy it online or at West Marine stores among others. https://www.jamestowndistributors.com/userportal/show_product.do?pid=3763
There are many more sources (Ebay) Pm me if you have a hard time finding it.
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I have used this stuff with some success
Black Epoxy Pigment (Colorant, Dye, Tint)
https://www.amazon.com/gp/product/B06XD39K55/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1
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Cool! Ordered!
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Not sure why any of this matters, won't you be filling and painting above the glue line anyway?
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You'll be able to see inside the cockpit; I'm concerned about glue squeezing into the cockpit and if it does, I want it to not show much.
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I have blackened my epoxy with india ink for years. Only takes a couple of drops, much more than that and it thins to much.
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Where do you get India ink these days? The death of manual drafting rendered it pretty obsolete.
Remember bow pens, dividers, rapidographs, drafting boards and T-squares. Circle templates, lettering guides, triangles and pounce powder. Scaling rulers, drafting pencils and rotary sharpeners. Power erasers, dusting brush, slide rule and velum. For the pro, a drafting head with degree angle adjustments on a parallelogram arm. Probably forgotten a few items lost in the mists of time. It was actually a pleasant form of art.
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Larry,
While manual technical drawing may be virtually dead, the art world still uses it. I have not had any trouble buying Rapidograph India ink made by Koh-I-Noor even fairly recently. My only issue with it is that it comes from Messychusetts.
Universal, Black India, 3080-F.BLA
The Divot
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For the curious: 30 minute epoxy with just enough charcoal in it to make it black (and still shiny) has barely more adhesion to sanded canopy material than 30 minute epoxy with enough charcoal to make it quite thixotropic. The stuff with lots of charcoal in it is stronger -- I suspect the charcoal is in small enough chunks to act as a reinforcement.
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Off topic but once technical drawing ink was mentioned;
Where can I find good ink for panel lines?
Standard Rotring ink is easily available, but there used to be a special type for Mylar film.
I still occasionally find single use Rapidograph cartridges but I’d love to find it in a bottle. L
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Back in 2016, in my famous GBR-3 build,
Page 5 Post # 208, I mention mixing artists acrylic water base paint, couple of drops, to 5 minute Epoxy, to attach the canopy.
"Extra, Extra!" Read all about it. Photos also.
https://stunthanger.com/smf/cfc-graphics/gee-bee-r-3-build!-semi-scale-cl-stunter!/200/
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You can get black india ink from Stewart McDonald, still made by the main manufacturer (no, I don't remember the name and it's out in the shop) that is used for, guess what, tinting epoxy and such. There's a near lifetime supply in a 6 dollar bottle from them. Google "stewmac'.
If you don't find it, email me and I'll link you up.
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Had a couple of minutes break, so will just post this now. Here's the site for the india ink. It's by Higgins.
https://www.stewmac.com/Materials_and_Supplies/Finishing_Supplies/Black_Fingerboard_Stain.html
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Will:
Thanks. I got some stuff that's specifically for epoxy, so I'm set.
It's probably overkill. I looked up the composition of India ink -- it's carbon black, originally lampblack, mixed with water and binders. So -- soot.
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That makes me wonder if I couldn't get the same results from the residue in the grill! As an aside comment, I am really enjoying your build thread Tim, thanks for sharing with us! H^^