I chose an easy part of my bike to "reflectablize" as one of my friends would say. A detachable fender that I mostly never detach.
Before we begin, I must state that I tried the two main manufacturers of "reflective spraypaint" on the market. Those being Rustoleum and Krylon. The amount of reflective material in the spraypaint was almost non existent. I found that I had to do way too many coats to even get noticeable reflectivity. I ended up seeking a refund from each company. Therefore, I strongly advise you NOT to waste your money. You could always go the reflective tape route but I found it to be expensive as well and just didn't seem as cool as what I am about to instructablize you on.
Step 1: Materials List
2) Krylon Clear Acrylic Coating (or similar clearcoat paint)
3) Masking tape (if you need to mask anything)
4) Paint tray or suitably sized object to catch glass beads
5) Empty spice shaker
6) Any necessary tools for disassembly of bike part
7) Retro reflective Microspheres (glass beads)
Step 2: Prepping the Part You're Painting
I also disassembled the fender to make masking easier, see photo.
Step 3: Fill Up the Spice Shaker With Glass Beads
You can source glass beads from several manufacturers / retailers. Google can help.
Note the gold spoon, this is a classy Instructable folks, no silver spoon here!
Step 4: Spraying the Clearcoat
I highly recommend you do a test run on a piece of cardboard to get a feel for exactly how it's done.
You will want to avoid a really thick coat, you do not want any runs, drips or pooling of the clearcoat.
The clearcoat I used stated it "dried in minutes" which ended up being a slight problem (I'll describe later). If you can find a non-quick dry clearcoat it would give you more working time to sprinkle the glass beads and re-sprinkle as necessary to get proper coverage.
Step 5: Applying the Glass Beads
I went with a thick coat, let it set for 10 seconds or so, then tilted the fender over the paint tray to let any loose glass beads fall off, many will. You only need a single layer coat of the beads, not a thick coat.
Allow the piece to dry fully.
Do NOT clearcoat over the beads, for best reflectivity they should remain uncoated.
When finished and dried the surface will look as if it has a winter morning frost on it, it's not particularly attractive but when safety is concerned I will take function over form.
Step 6: Reflectivity Test!
The photos speak for themselves really, the fender turned out quite reflective I must say.
Step 7: Wrapup / Future Ideas
As I have disc brakes on my bicycle my next application will be on the rims. I have yet to find a tire that I like that has reflective sidewalls, many manufacturers just don't do reflective sidewalls.
My next experiment with adhesion of the glass beads will probably be using an industrial 2 part clear epoxy which takes much longer to dry and should provide much better adhesion for the glass beads.
You could also use a colored paint to adhere the glass beads, there's no reason it has to be a clearcoat. Rattle canning your old bike frame? Why not make it reflective too!
I will also be doing this to the # sign on the front of my house so the numbers are reflective, just need to do a bit more masking.
Thanks for your attention!