Your work sounds really interesting and commercial. In my experience, one of the biggest problems is finding a market for your products. No one else can do this for you, unless you know another maker with similar type products. Some 'craft' is easy to sell, but others struggle. Remember 'Craft' means many things to many people. There are so many different types of craft for example, that I think it's difficult to market them under one roof.
In my experience the more you spend on space, does not equal more sales. It might, however, promote and showcase your products if there are lots of visitors. Sometimes relatively cheap events (£10+) can be good selling venues. I think it makes sense to start at this level and then spend more as you discover who is your customer (age, sex, type etc) and which products sell well and have a good profit margin. At County Shows there are lots of visitors, but only a few visit the craft marquee, and even fewer make a purchase. I think some of the big events, have too many attractions/distractions and visitors haven't enough time to see everything. Craft fairs, on the other hand are smaller, and attract people interested in all sort of crafts and handmade goods. However, that is the problem. The visitors won't always want to buy glass. Ideally you need a 'glass event', just as potfest is just about selling 'ceramics'. Sounds mad, but at least you know the visitors are paying to come and see and buy 'glass' and only glass.
I would suggest you take a range of glass products to your first show, to find out your best seller. Don't forget to spend some time building an eye-catching display as this is really important if you want to add value to your products.
LH
17 Mar '07 - 9.08pm