Best practice guidelines for the design, production and presentation of vacuum formed tactile maps

Reproduction technology

When the purpose of the map has been identified, the most suitable reproduction method can be chosen, but it is likely that many designers will not have access to a range of technologies. When vacuum forming is to be used, the most appropriate type and grade of plastic foil (sheet) for the purpose of the map must be considered. The grade of foil to use depends on the maximum height of the reproduction. Many maps are reproduced in 100 micron (0.100mm) PVC but this is not substantial enough to resist finger pressure during reading when symbols are higher than about 2.0mm. For most maps with symbols up to 6.5mm high, 200 or 250 micron gauge (0.200-0.250mm) PVC gives satisfactory results. The thicker material offers greater rigidity without any apparent loss of definition, and therefore is the material of choice in most cases. If transparent PVC foil is used, a printed underlay can be incorporated into the finished product (see Figure 8).

However, when people with some residual sight need to locate a map from a distance, as in maps on golf tees, it may be preferable to use opaque, bright yellow, PVC foil (see Figure 9). Alternatively a bright yellow underlay could be used (bright yellow is the colour recommended by RNIB as being the most visible for many partially sighted people).

Opaque PVC foil can be printed before it is vacuum formed, but this is a costly and difficult process. The printed image has to be accurately registered with the raised map design, and the amount of deformation of the plastic foil has to be taken into consideration when the printing is carried out (see Figure 10).

If maps are being designed with mould heights greater than 6.5mm, a heavier grade of PVC foil should be used. Maps that represent contoured hillsides may have mould elevations up to the maximum that the vacuum forming machine can accommodate. As a guideline, total mould heights between 6.5mm and 20.0mm are best reproduced in 500 micron (0.500mm) PVC foil (see Figure 11, [*]), and elevations greater than 20.0mm are best reproduced in 750 micron (0.750mm) PVC.

1.0mm thick acrylic sheet also works well for many images with heights over 6.5mm (see Figure 12, [*]); success depends on the map design and it is recommended that a trial copy is made before deciding on the material to use. Before forming maps higher than 6.5mm it is necessary to spray the plastic film with a silicone release agent to facilitate removal of the map from the mould.