Faux Rust Signs Made "In the Name of Science"

[eaglesplsh]

Hearing about Ted's MAKEcation inspired me to set aside some time during the holidays for having fun. When you work with these tools to cut the same types of parts and materials every week, it’s easy to forget how they can empower your creativity. It’s hard to believe that I don’t spend more time goofing off with the bot. These side projects brought back all those feelings of excitement that I first had when starting out with CNC machines.

I've always been fascinated by the patina/faux metal finishing examples that Bill Palumbo and other botters have brought to the ShopBot Camps. This seemed like the perfect project for playing around with some of these techniques.

The signs shown in the pictures below were inspired by props used on a popular science TV show called “Mythbusters”. The originals from TV are made of steel and every week they get burned up in an explosion, covered in cockroaches, dragged behind a car, etc… all “in the name of science.” My signs are just made from TRUPAN with a faux rust patina. And, they’re doomed to even worse carnage - they were made for use in the 8th grade science classes that my brother teaches.


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Click here to view the full size pictures. (https://www.dropbox.com/gallery/2427786/1/Mythbusters%20Signs?h=60dd08)

I created the vector files from scratch, using an open source font, so they’re just loosely based on the originals. The cut files were simple – just pocket around the letters 3/16” deep, and profile around the outside edge. The messy font edges gave me a chance to try the “rest” machining feature in PartWorks for the first time – made it easy to clear most of the pocket with a 3/8” bit and then come back with a 1/16” bit to do the detailed nooks and crannies. I switched to an 1/8” bit for the outside profile.

Because Trupan is so easy to cut I decided to see how fast I could cut with the smaller bits. I ended up at 3 ips for both cutters without any problems. DOC per pass was 0.1875” for the 1/16 cutter and 0.250” for the 1/8” cutter. Speed was set to the fastest setting on the PC router – rated at 21,000 rpm.

This brand of iron paint/rust accelerator is common in many craft stores. I ended up buying from these folks who sell it in larger quantities:
Iron Paint (http://www.tricoatstore.com/store/product.php?productid=16151&cat=253&page=2)
Rust Accelerator (http://www.tricoatstore.com/store/product.php?productid=16180&cat=254&page=1)

The paint job was simple – just slap on one coat after another. I didn’t even have to worry about drips/runs. It did take a long time to make sure you got into all the tight areas, and there was a lot of waiting for things to dry and wondering if/when/how the rusting magic was going to kick in. Since I rarely do any type of finishing, this part stretched my patients at times – I don’t think I’d make it as a sign guy!

I started with a latex primer, which made the TRUPAN fuzz up. Thankfully, the fuzz just added to the rust texture, so it worked in my favor. Next came a generous coating of the iron paint, followed by spraying/spritzing with the rust-accelerating acid. Basically you’re supposed to let the iron paint dry some, but not too much. If it dries too much it won’t react with the rusting acid. That’s where the directions for the product breakdown. If you read the website, the box, the back of the bottle, and independent reviews on the web, they all tell you to wait a different amount of time before applying the acid. I ended up letting the iron coat dry 12 hours. I’m really happy with the results I got, but the next time I use this stuff I’m only going to wait until the iron coat is dry to the touch – I bet you could get similar results with about 1/10 the amount of acid that I ended up using.

If you haven’t already tried the faux metal paints for yourself, I’d highly recommend you make some time to play around. They really are easy to use and they produce amazingly realistic results.

[myxpykalix]

I too was amazed at the results we saw at the shopbot camp when bill let us try our hand at it. There was one piece there that looked like an old brass item, then you pick it up to realize its a piece of foam!

The only way to tell your part isn't a piece of rusty steel would be to pick it up. Good job.

[john_l]

Neat project Russ. How long after you apply the acid does the rust appesr? Howlong after applying to be able to handle the piece?

[wberminio]

I saw these in person.
They are truly realistic!
Keep up the good work-Russ

[eaglesplsh]

@ John L -
Waiting for the rust was the nerve racking part... The cutting went real fast, but between the primer and the iron coat I spent many hours painting these things before applying the rusting solution. (It may be hard to see in the pictures, but they're really 30 inches long with 4" high letters.)

I think the directions said it would be fully rusted in 10 minutes. But, it took maybe 45 minutes before I started seeing even the slightest sign of rust. Between the time put in and the $$$ spent on the paint, I was starting to get pretty annoyed, thinking I had received old product.

To get what you see in the pictures, I had to recoat with the acid every 30 minutes for several hours - I applied a heavy spray each time and basically kept the surface constantly wet until I ran out of acid.

I found that the backs of the signs rusted faster/more from just one acid spray than the fronts did with a couple applications. The backs still had the TRUPAN skin on them - perhaps that kept the material from soaking in as much or kept the iron paint from drying on that side, leaving it more reactive.

I was working in my basement, which is probably around 60 degrees. I have since wondered if the room temp needs to be 70+ to kickoff this process quickly.

The mfg recommends waiting 24 hours for the rusting process to complete before clear coating. I didn't bother clear coating these. You can handle them once the acid dries, which takes about 30-60 minutes after the final application.

One more detail to share with anyone who wants to try this stuff for the first time - I found it very difficult to control the rust color/texture. If you're trying to create a matched set of something, make sure you are working on all of the pieces at the same time/in the same amount. If you look at the pictures, you'll see that once sign is much darker that the others. That one was actually the lightest/most colorful of the bunch at one point. I was running out of acid, so I stopped spraying it and just did the others - I guess the chemicals hadn't finished reacting when I stopped the application and now that one doesn't match the rest of the set.