Swell Paper

This sub-web contains information on "swell paper" (aka capsule and/or microcapsule paper) and related products.

Motivation

Swell paper has a special coating of heat-reactive chemicals. Microcapsules of alcohol implanted in the paper fracture when exposed to heat and make the surface of the paper inflate. Placing black ink on the paper prior to a heat process provides control over the raised surface areas.

-- Tactile graphic (WP)

Swell paper is considerably more expensive (about $1/sheet) than regular (or even braille) paper. However, it is far more precise than embossed paper or plastic and much cheaper and faster than laser engraved plastic sheets. Unfortunately, it is not optimal for long-term use:

Capsule paper dries out quickly and is also damaged by too much moisture. Store tightly sealed and away from direct light and heat sources.

-- Microcapsule Paper and Fuser

Although swell paper can be used on its own, it has also been used on conjunction with other devices. For example, the talking tactile tablet (T3) uses swell paper to create overlays for a touch-sensitive graphic tablet. Audio response provides feedback when regions of interest are touched.

Making a Machine

Commercially available swell paper machines aren't cheap; typically, they cost around $1500. This makes casual experimentation pretty prohibitive, but it also limits the number of Real Users (TM) that can afford one. In addition, they require a separate printer, adding cost and complexity. So, I'm working on making my own.

Light Source

The machine needs to expose the swell paper to a bright light source. Commercially-available fusers tend to draw about 600 W, so I suspect that they use something like a laser printer's fuser lamp. I acquired a used laser printer ($10 on Craigslist :-) and pulled it apart. As I had hoped, the fuser tube contained an 11" long halogen lamp.

Although similar lamps are available on eBay, pulling one out of a laser printer has the benefit of providing the specialized connection clips and associated high-temperature wiring that the machine will need. There will also be other parts which may be useful. For example, it might be possible to reuse parts of the paper feed mechanism and drive electronics.

Cautions

If you decide to follow my lead in this area, please be careful! The lamp runs on AC wall current and gets very hot; please don't electrocute yourself or scorch your fingers. Even when the lamp is cold, it requires careful handling. Being delicate, long, and skinny, it would be very easy to break.

Also, be sure not to touch the lamp directly. Any oil that gets onto it (e.g., from your fingers) can burn during operation, heat up the glass, and cause the lamp to break. (FWIW, I used a paper tissue to protect the lamp from skin contact.)

Initial Version

For simplicity, my initial (manual) version had no moving parts at all. It was basically a wooden box (12" x 4" x 4") with an open bottom. The contents included the fuser lamp, a sheet-metal "mirror" (hand-shaped into a trough), a 3" exhaust fan, and associated wiring. For safety, I covered the opening with 1/4" mesh "hardware cloth" (loosely woven wires in a simple rectangular grid). Finally, I added some feet to make room for sliding the swell paper underneath the box.

My usage plan was to:

  • place the machine on a (heat-insensitive) surface
  • slowly slide a sheet of swell paper under it
  • inspect the results and repeat as necessary

In practice, however, I found that the paper curled up into the box and jammed. I worked around this problem by standing the unit up on one end (facing away from me; that lamp is really bright! :-). Conveniently, this also allowed me to inspect the results in progress.

That said, I'd still like to be able to use the machine in the "intended" manner. So, to give the paper more room, I made the feet a bit taller. I also plan to experiment (Real Soon Now) with stiffening the paper (e.g., binding it with paper clips to a stiff cardboard sheet).

Futures

It would certainly be possible to manufacture a more polished version of the manual unit. The primary advantage of this would be cost: If the parts could be purchased for about $25, the finished unit could sell for $100 or so. However, such a unit would be inconvenient to use, particularly for a blind person.

Ideally, the machine could print and expose the paper in a single, automatic pass. The basic mechanism could be taken from an economical ink jet printer (e.g., low resolution, monochrome, USB). Cost aside, this avoids a problem that swell paper can have with laser printers: if the area around the fuser gets hot enough, unprinted microcapsules can swell.

Swell paper is fairly stiff, so the feed mechanism would need to have a straight paper path. After the ink is applied, the paper would be exposed to the fuser lamp. The feed rate would need to be appropriate (and reasonably consistent) to achieve proper exposure times. So, the printer electronics would need to buffer the entire page image.

Resources

Vendors


This wiki page is maintained by Rich Morin, an independent consultant specializing in software design, development, and documentation. Please feel free to email comments, inquiries, suggestions, etc!

Topic revision: r70 - 04 Sep 2016, RichMorin
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