I thought it might be worthwhile to add comment about access to objects for the visually impaired visitor.  I have been working on a series of CD based audio guides for museums in the north west of England (UK) where from the outset areas of 'tactile experience' have been identified.  The museums vary from 16th, 17th century country houses, a maritime museum, a reconstructed Victorian street, an industrial gallery, and latterly a museum gallery featuring an Egyptian mummy.
In the country houses the exploration of the shape and size of doorways, curtains, carved chair backs, wooden panels, window lights, furniture are in included in the tour. In the case of the mummy gallery, specially prepared raised-surface tiles are arranged on the wall allowing guests to explore the shapes of the hieroglyphs. In the maritime display, a fibreglass cast of large fish some 6 feet long caught by local fishermen is on display.  Pegs or markers are included on the outside of the case so that the length of the fish can be determined by the visitor.  The look on their faces says everything!. Where items might be contaminated with acid and fats from finger ends cotton gloves are supplied. There is also the issue of personal safety - crashing your head on a low 17th century door frame should not be part of the visitor experience, correct guidance and safety information is vital.  In a several museums we also supplied magnifying glasses to enlarge the view of objects behind glass, as well as 'approved' electric torches for use on objects in low light conditions.  Before any of these approaches are used a risk assessment is made, and decisions taken both by the curator and the conservator. 
In the UK most registered visually impaired visitors will have some residual vision and this brings into play other elements of museum work worthy of exploration on the List - for example design, the need to create areas of light and dark contrast in displays.
 
It is not, in my view, just straight forward access to objects that is important, but the whole experience. There is no substitute for exploring the size, shape and smell say of a steam locomotive, the layout of a castle or the shape, the size and intricacy of a carved wooden panel, the sounds of a creaking wooden floor, or handling a Nautilus shell.   Duplicate object collections are a good idea but should complement, when possible a wider experience.
 
If anyone is interested further I am always happy to give details off line.
 
Ken Howarth Heritage Recording UK 
www.hrec.ndirect.co.uk
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