Out of the tin it’s a little underwhelming, it really is!
Everyone needs a Yoda or Stormtrooper, now imagine you do and it looks as if you’d had bust cast in solid bronze – enter ColorFabb’s Bronze Fill filament. From the outset you don’t get to enjoy the metallic luster of aged bronze. The material has a somewhat earthy appearance somewhere close to mud – no sparkle, no bling, nada. The magic lies in the post production, to coin a phrase. The printing is only the first part of the process.
Printing with 1.75mm filament is a cinch. It layers down beautifully at a moderate print speed, don’t get impatient when using this material. It’s a lot heavier than other filaments with a much lower tensile strength, so too much speed and tension on the spool will leave you disappointed and frustrated with breakages and failed prints, yeah and this stuff does come in at a little bit of a premium.
Adjacent is the result of some fun and games and the final result of a few techniques used to get the bronze look you would expect to see. The photo doesn’t do the bust enough justice but what happened here is the following:
Software: Simplify 3D
3D Printer: Leapfrog Creatr Dual Head
Temp Nozzle: 185° C
Temp Bed: 35° C
*model downloaded from Thingiverse
Upon completion let it cool. Bronze Fill although printed at a high temperature it has a low plasticizing temperature – this was discovered by mistake – nearly a big one too. The plasticizing temperature seems to be as low 65°C, so make sure your print has cooled to room temperature before you start the following process where you’ll need the following:
Braso polishing compound,
Dremel with detail abrasive brush attachment,
Oven proof glass casserole,
Small oven proof bowl – small like in egg cup sized,
Step 1 – Print
Step 2 – Surface preparation
Buff the surface of the model with the detail brush on a Dremel or similar speed controlled engraving tool. Not too fast as the friction between the brush and the model will cause localized re-melting of the material. I found this to be the perfect first step as it allows you to give the model an all over general roughening up, exposing the bronze particles below the surface. Once you’re happy with the level of buffing, use the steel wool. The steel wool doesn’t get into the corners as well as the buffing wheel, which creates layers of exposed particles, which in turn allows for varied levels of oxidation adding to the character of the final model.
Step 3 – Buff
Add a little brasso to the mix when you buff with steel wool. This will react with the bronze particles and the print will start developing some of that green characteristic synonymous with cast bronze. Avoid being overzealous with the Brasso. In earlier tests it was found that the Brasso can degrade the print which resulted in delamination between the layers. Once you’re happy with the results, take some Brasso on a polishing cloth, a tiny amount which has dried, and give the model a thorough wipe removing any excess Brasso used in previous steps.
Step 4 – Ozidize
*This is a messy and smelly process and has a hazardous component to it. You need to exercise caution and common sense here.
Place the model and small bowl containing some oxidizing solution into the oven bag (use a double bag) and place it in the caserole. Before you seal the bag completely inflate the oven bags to prevent it from touching the model, seal it up and stick it in a preheated oven. The oven I used was preheated to about 75°C. Watch this step closely, the process is quick and takes only about 5 minutes. The oxodizing fluid will form a vapour cloud which then oxidizes the part – the part will turn black, how black, well that depends on how long you leave it in for.
Upon removing the part, you may want to have a pair of gloves on, the condensation on the inside of the bag is acidic and smells like egg – really bad egg, and is probably bad for you, so try avoid too much skin contact. With the blackened model in hand use some steel wool to lightly buff the areas where you want to brighten up the ‘casting’ and also the Brasso covered polishing cloth used earlier.
Play around with this and the results are pretty cool. If you have any questions drop a note in the comments and I’d happy to help.