Father of the RepRap and nearly all things DIY 3D printing has managed to bypass the tyranny of the triangle to 3D print directly from OpenSCAD's CSG representation without using an STL file in the workflow.

What does this mean?

Printing directly from CSG is much more robust than using the flakey (literally) STL file format.  A CSG file can be wrong - we can all make mistakes - but, unlike STL, it always represents an unambiguous solid.
It should also be faster (5%)........  Finally, it should allow us easily to do fancy things like filling solids with scalar and vector fields representing build parameters, so you can have an object that is flexible (and/or green) at one end and rigid (and/or blue) at the other.

Visit the RepRap Wiki for instructions on how to use this process on your RepRap.

Perhaps this will actually pave the way to better communicate multiple materials to Objet 3D printers which currently require multiple STL files to create multiple material parts?  

Thank you Adrian

Shapeways community member Erckgillis has shared some great tips on how to patina 3D printed Silver using Liver of Sulfur, along with some patina processes for other metals.

Patinating Silver

While Liver of Sulfur is usually used to form a black or gray patina on silver, there are a number of intermediate interference colors formed, especially if a weak solution is used. These include yellow, reddish brown, purple and blue. Some people recommend adding a small amount of household ammonia to the solution claiming it intensifies the lovely blue-green-red-purple interference colors one gets when using a dilute solution and slow approach. These pretty colors are not very stable over time because they continue to react with sulfur in the air and darken. You can sometimes 'save' them by spraying a lacquer over them. They may be retained if the surface is properly sealed. Acrylic resin is the recommended sealer for durability and resistance to darkening in light. Some jeweler's lacquers also work. Envirotex® works very well for this.

Using Liver of Sulfur on Silver

1.Take a piece of Liver of Sulfur, about the size of your finger nail, and dissolve it in a cup or more of warm water.

2.Heat the piece of metal to be treated and then dip in the Liver of Sulfur solution.

3.Rinse in water after each dip. While Liver of Sulfur is usually used to obtain gray and black colors on silver, there are a number of intermediate interference colors formed, especially if a weak solution is used. These include yellow, reddish brown, purple and blue. Some people recommend adding a small amount of household ammonia to the solution claiming it intensifies the lovely blue-green-red-purple interference colors one gets when using a dilute solution and slow approach. These pretty colors are not very stable over time because they continue to react with sulfur in the air and darken. You can sometimes 'save' them by spraying an appropriate lacquer over them. They may be retained if the surface is properly sealed. Acrylic resin is the recommended sealer for durability and resistance to darkening in light. Some jeweler's lacquers also work. Envirotex® works very well for this.

4.The piece may be sanded lightly and polished. Raised areas will show the original color of the metal, recessed areas will remained blackened.

5.Be sure to wear gloves and protective clothing when working with Liver of Sulfur. The fumes are dangerous and it should be used with good ventilation and covered right after use. It must not be allowed to come in contact with acids as a toxic gas is then rapidly evolved.

Michael Mueller has used another post production technique on his silver 3D prints to give them a little more character. See the before and after below.

If you want to try this for your own ... if you need some hints... ... There are also a lot of links in the web how to do this. All you need is a glass, water, salt, wire and a 12 volt dc power supply. 

Sounds like dangerous fun... For a slightly less electrically charged option you could try Mark Cheng's methods.

Tom Kluyskens of Made on Jupiter has made the perfect, Sweet As! wedding gift using Shapeways 3D printing. Not satisfied with the standard coffee maker, kettle or toaster as a gift, Tom designed and fabricated a tie and bracelet in the wedding theme of Sweet As!

The pieces were modeled parametrically in Houdini (a high end digital film effects tool), and the resulting 3D model was sent to Shapeways for 3D printing. We (digitally) engraved the two key sterling silver pieces with the theme of the wedding:

Take a look at Tom's post that steps through the process including a video of how the tie was set up in Houdini, really interesting to see node based architecture for 3D modeling.

All images by Tom Kluyskens, see all project images on Flickr