A sign for the Garden

A front-yard garden often results in a lot of passers by asking questions or compliments. I try my best, but people are...difficult...for me so I try to muddle my way through. After the last few years of this, I started to think it might be nice to put up a webpage for the garden as a way to collate questions, answers, as well as post pictures.

I eventually put up that page: deninet.com/plants, but who would find it? This got me thinking about making sign for the page. The idea was simple enough; a QR code for easy smartphone scanning but with a human-readable URL to make it clear what the QR code is.

There are lots of QR code generators out there which you can use for free. Many require no signup for the most basic of features -- mostly just generating the graphic containing the QR code. Many offer additional features like frames, text, or logos given a payment or a signup.

Fortunately, I didn't need either. All I needed was something that could generate the QR code as an SVG graphic file. The process worked like this:

1. Generate a basic QR code for the URL with no frame, text or logo.
2. Export the QR code as SVG.
3. Import the SVG into the open source editor Inkscape.
4. Add a background shape and text.
5. Export the edited graphic as a high resolution PNG.

That got me an image which is black and quite. The text and QR code being black, and the background shape of the sign in white. Being a PNG, there's actually a third color: transparent. This allows the corners of the side to have a gentle curve.

Once I had the PNG, all I had to do was import it into my preferred 3D printing slicer, Cura. Cura has a feature known as lithophane, which takes a grayscale image and converts it into a height-map for 3D printing. Typically, white is the lowest height, and black the tallest, with levels of gray in between. Transparent pixels in the image aren't printed.

When importing the image, you configure Cura the height of the base (white), and the total height of the print (black). I configured the base for 2.5mm and the total height 5mm. After that, I had a very nice sliced model.

The problem is, I have an inexpensive 3D printer which can only print one color at a time. I could have faked a multi-color print by changing the filament mid-print, but I had no white filament on hand anyways. What I did have was some Golden Open Acrylic paint.

I've used Acrylic paint on 3D models before. While the Golden Open type takes forever to dry it does tend to stick to the comparatively rough 3D printed surface well. So, with a brush and a careful hand, I hand panted in the QR code and text. Each coat only took about 20 minutes to do, but I had to be careful not to mar the base with white paint. Doing so might create errors which means QR code readers couldn't interpret the image.

With this done, I needed a way to mount the sign outside. The first was simple. We have a number of purple garden poles which we use to support tall and climbing plants in the garden. Using a hot knife, I created two pairs of slots in the base of the sign through which I could slip a zip tie. Two zip ties and one pole, instant garden sign.

A second, more difficult problem was making the sign -- and more importantly, the paint -- durable in a Minnesota summer. While the print itself would likely survive, the paint may degrade quickly without further protection. For this, I got some clear spray paint which was designed for plastics from a local hardware store. After applying multiple coats, the sign was as durable as it was going to get.