Also Known as: Vacuum forming
Technologies: C.R.Clarke, Braillon
Principles: Collage master covered with plastic, heated and vacuumed
over the original to create a copy.
What is Thermoforming?
Thermoform diagrams are created from a process where
a sheet of plastic is heated and vacuumed on top of a model or
master. The master can be made up from almost anything, although
certain substances can be more durable than others.
How to Make Thermoform Tactile Graphics
The key to a good thermoform tactile graphic is
in the creation of a good master. Masters are generally built
up from a base of card, but the card must either be thin enough
for air to pass through it, or small holes will need to be drilled
through for the vacuum process to work.
A sketch of the design can be made and transferred
onto the base, from which outlines and regions can be built up
using a variety of materials.
To give substance to a tactile graphic objects such
as balsa wood or card can be cut and glued in place. Some of the
more artistic thermoform master designers use ceramic tile cement,
which can be manipulated to the desired shape.
Braille can be added by cutting and pasting sheets
from a standard embosser or Perkins machine.
Where to buy materials and equipment
Braillon plastic sheets can be purchased from RNIB,
or the American Thermoform Corporation.
Thickness: Light (100 microns), Medium (200 microns),
Heavy (300 microns).
Vacuum forming machines can be bought from C.R.Clarke.
Materials for making a master can be found almost
anywhere, and common materials include string, balsa wood, card,
wire, beads and wallpaper.
Links to Suppliers
Details
Techniques
There are four variables to consider when thermoforming:
1 - the weight (thickness) of the plastic
2 - the temperature of the heating element
3 - the length of time the diagram is held under the heat
4 - the time the vacuum pump is on
The balance between these variables is critical,
and exact settings vary between machines, negating any possibility
of definitive instructions. There are however basic guidelines
which will allow you to find the optimum settings with the minimum
amount of wastage.
Plastic sheets can be re-heated so long as they
have not reached their critical temperature. Start with a medium
temperature and short times, you can lengthen the times and increase
the temperature experimenting with the same sheet of plastic without
it burning or crinkling irreparable.
Standard braillon plastic sheets are designed to
be thermoformed smooth side touching the master, and the slightly
bobbled side up.
If a master has a thick base, or is built up over
many levels, you may need to drill small holes through to allow
the vacuum to be developed around the master.
Masters can start to degrade when used to produce
many copies in one go. Allowing the master to cool a little after
10-15 copies can help to prolong its life.
Ann Gardiner and Chris Perkins have written a set
of best practice guidelines for the design, production and presentation
of vacuum formed tactile maps. http://www.art.man.ac.uk/Geog/tactileguidelines/
Tricks of the Trade
Try not to use rubber based glue or items in the
creation of masters. They are more likely to melt under the heat
of the thermoforming process.
Thermoform - strong points
- Good height & texture variations
- Easy to produce multiple copies from one master
- Different paper weights allow for high definition images
- Durable, wipe-clean pages
- Braille text is easy to make
- Each copy is cheap to make (paper 8p-40p)
Thermoform - weak points
- Labour-intensive to make collage
- Requires craft materials and skill
- Not easily visible when thermoformed so may not be ideal for
partially sighted individuals
- Fragile masters: storage and repair issues
- Machine is expensive (start around £2-£3,000)
- Limited to 11 x 11 on non-industrial machines
- Slow reproduction speed
- No colour, no print, unless written on afterwards
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