There probably can't be that many spiders down here. Probably. Create this by using other Rag Trade items in your inventory.
Purchased for 2 pence, Sells for 1 penny
Using Silk Scrap
Sell off a few yards of silk
Off to Spite, where the rag markets open early.
Swap spiders-silk for surface-silk
The Marred Mercer is one of the few Spite market-men who will deal with outsiders. [This will always gain you Surface-Silk Scraps. There may be other effects.]
Unlocked with 100 x Silk Scrap
Swap a great deal of silk
'Now that's a good few bolts and no mistake. Right, surface-silk you say? Best sharpen me shears.' [This will always get you many Surface-Silk Scraps.]
Unlocked with 1000 x Silk Scrap