: Paper that reflects car lights? Or glows in the dark I have an assignment at uni that requires me to think of a way to make a flyer work as an accessory. I chose to design it as a reflector

@Alves566

This type of device or coating is called a retroreflector. A home repair store (or bike store) will probably have spray-cans of clear reflective coating, or you can use a retroreflective paint as a spot color.

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@Margaret771

Traffic signs have a thin, specially roughened reflective aluminium sheeting that bounces the light directly back where it came. The aluminium is not bare but has a protective tansparent coating that also acts as the color, if needed. Arbitary figures can be made by cutting. Printing or painting on it should be possible, but it surely is a challenge due the very different nature of the reflection when compared to paper. Black print surely is a no-problems case, but color and halftones need some investigations.

That material is not visible without lights in the dark and light makes it best visible to that direction where light comes from.

By mixing small glass or plastic prisms or balls with transparent lacquer it's possible to make reflective paint. It is used at least for on-road markings (streets, highways). It's useless to paint uniformly over an existing print.

Self-illuminating colors and materials exist. They collect daylight as ultra long life electron state exitations that gradually collapse as emitted light.A car can refresh a faded light. The contrast is low and the effect is nearly unnoticeable in the light. Its like glow worm light. I've seen no printable inks that use this principle.

Have you ever noticed, how strong is the color of the safety vest that an on-street worker keeps on? It's color is the one that converts daylight to a narrower wavelength band. That band gets a boost. It's called "fluorescent color". Fluorescent inks are available for printing. They are not not visible in the dark.

One form of fluorescent ink is the one that glows in UV light (=black light ink). It needs an ultraviolet lamp to become visible. At the same cost you could easily illuminate your poster by a normal lamp, but without the glow.

The last one is electroluminiscence (=EL) Those inks glow when they get electric current. see an example: www.dupont.com/content/dam/dupont/products-and-services/electronic-and-electrical-materials/documents/prodlib/MCM-EL-Processing-Guide.pdf Electroluminiscent inks and materials are an old invention. In the past many hobbyists made own EL inks by mixing zinc sulphide with water and some other chemicals.

Extra: Fluorescent inks have gained popularity as tattoos, because there are so many places where they can make a stunning effect. For EL inks this propitious places are rare and not especially wanted to get in.

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