If you get on the login page at first, click on the accedir com usuari extern and change the language into English on the lower left corner of the page. After that, click on the Imatex link on the left and search link will appear underneath. On the search options I've chosen "Thesaurus" and searched with the word "18th century" for most records of the period. If you're not so particularly interested in pieces of fabrics, you can simply go to page about 50 and you'll find pictures of whole outfits and garments there. The search is a bit slow, actually, but what's great is that the zoom is really great bacause you can take a very close look at the garments.