The Institute of Making hosts the Materials Library, presenting a collection of all sorts of materials from synthetic or natural sources, comprised of just about any material you could possibly think of.
The Materials Library was opened in 2005 and now has occasional open days where visitors can explore the collection.
You will need to join their mailing list to find out when open days are planned.
UG: Goodge Street 0.33km
UG: Euston Square 0.35km
UG: Warren Street 0.42km
Check Website for opening times
Always check details regarding opening hours, accessibility and pricing before travelling.