Thanks everyone for the kind words on the builds.... They were really a lot of fun. I'll talk a little about the R2 Blue and try to guess/answer some of the questions.
I had decided that the R2 I wanted to build was a replica of the R2 as seen on the first day of filming for Star Wars at the Sandcrawler scenes. There are some unique differemces on that droid in paint and configuration and as I figured it that was the closest R2 was in the films to how the original builders intended him to look.
The blue has always been a major question for builders. It appears to change radically from scene to scene and even moreso from film to film. There are hints of purple in ANH and some very strong and interesting highlights going almost black off axis. That has been a very tough look to replicate with paint. I'm going to be running through a bunch of stuff here. If I miss something feel free to ask questions. I'll answer them if I can.
First, we know what color R2 was painted in the new movies thanks to a VERY well informed source. We call that Hypo Blue. Its based on paints from House of Kolor with a mix of metallic colors for a basecoat and a candy blue top coat. The exact ratios and technique are available on Astromech.net
It is my belief that the "Hypo Blue" color for the new films was to replicate the look of the droids in the archives at Lucasfilm, the bulk of which were painted (or repainted) for ESB and ROTJ. The droids in ESB and ROTJ were largely fiberglass so a lot of the silver details were painted on the bodies. the blue details on those bodies were also basecoated with a silver then topcoated with a candy blue paint. This can be seen in a lot of reference and I was able to verify through one of the original ROTJ era R2 guys that the candy blue was special irdered from a supplier in the US. (exact supplier unknown)
The Blues in ANH appear distinctively different from the other films.
The difference on the ANH era droids is that they were largely built of aluminum, not fiberglass. A lot of folks have been trying to figure that out and we had the same challenge. Mike Verta had done an amazing R2 build a few years ago and the blue was a big part of the look for his droid as well. Talking to Mike about the type of reflections that appear on the ANH R2 it became obvious that the blue was a transparent blue applied directly over the raw aluminum on the ANH droids. It has a very distinct look and gives the almost black off axis reflections just like in the film. Part one solved. It was a transparent blue of some sort. Now we had to figure out what the blue was.
Matching the exact blue hue was tough. Everything I tried seemed too shift the color too much to purple or green never giving the right black darks. Experiments with a lot of color tints also seemed to thick on the aluminum and never really adhered well. (Aluminum doesn't like to take paint.)
It wasn't until looking through a thread on Astromech where kimncris was machining some of his own aluminum parts as just mentioned above and using a machinist layout dye that it all fell together. The blue of the dye was perfect! it matched the highlights, had the dark blacks, in some shots a slight purple tint, and the thickness issue seemed to be totally gone. Its basically a permanent maker dye.
There are a LOT of machinist marking dyes out there and I started researching as many of them as I could get my hands on. This pic shows some of the test samples....
http://www.partsofsw.com/RPF/R2BlueTests_01.jpg
I kept coming back to the DYKEM brand Steel Blue dye. (the two left most samples in the above pic) The same stuff Kimncris was using. Strange but true coincidence. That brand, different than the others, also has a brushable AND rattle can version. It seemed perfect.
THEN while gathering reference for an official illustration project I came across an amazing photo from Lucasfilm. It was from the model department for ANH and they were painting a miniature of R2 to go on the landspeeder model. He is painting the blue on R2. In the foreground... a rattle can of DYKEM Steel Blue layout dye that has been sprayed into a cup the model maker is using for brushing on to the model!
Another behind the scenes photo shows the original R2 under construction out of all aluminum with the Blue Dye in use on the dome for marking panels out for cutting.
One problem with DYKEM, even on the original droid is that it is not lightfast. It shifts pretty dramatically with exposure to sunlight. That IS fixable but it requires the application of a UV protective topcoat.
Problem two with DYKEM is that in person, because of the pigment, it appears very purple especially under incandescent light. It still photographs really great though and looks fantastic in photos. (The prussian blue pigment doesn't reproduce in the RGB colors of our displays or even very well in traditional photographic processes)
We didn't want our droids to look purpleish in person even though the DYKEM is in all likelyhood technically correct so we had to find an alternative. What we came up with after a bunch of testing was an automotive clearcoat with a candy blue tint mixed into it. The color we found and ended up using is a Dupont Hot Hues True Blue Candy Tint that we mixed into our clearcoat. Then sprayed through an airgun in multiple coats until the desired darkness and color were achieved. It photographs virtually identical to the DYKEM Steel Blue yet looks great in person.
Thats the story of our R2 Blue.... Hope that makes some sense of it all.
