Reading a recent post by Jeff on Angler's Post I bought a smaller set of scales than my normal dial set. I've never been too happy about lighter weights - say 5lbs and below. So looking on eBay I got a set of Berkley Classics, a digital set reading up to 15lbs. Following Jeff's experiment I first of all measured 16 fluid ounces of water into a large glass jug, making sure I took the bottom of the two lines as the reading. I zeroed the scales with a medium freezer bag from Sainsburys (plug) and weighed the 16 oz. The scales read 1lb 1.5oz. I re-checked the measurement in the jug but it seemed OK. Then I poured the water into 2 smaller Pyrex jugs and found that this amount of water was nearly 18oz. So much for measuring jugs from an unknown manufacturer!
I reduced the water to 16oz in one of the Pyrex jugs and re-weighed. The scales read 1 lb exactly. Happy days.
All I've got to do now is get out and catch some fish.