Making it float
When anglers used relatively short lines - the vast majority of flies were fished less than twenty feet from the rod tip until the end of the 18th century - there wasn't much need to make flies float, because they could literally be dangled on, or just under the surface. However, when longer braided lines came along and, in particular, when anglers made the move to silk lines, their tackle began to sink, dragging the fly under with it and so all kinds of ingenuity had to be applied to making it stay on the surface.
The first move in the long drawn out war against waterlogging was to build buoyant materials into the bodies of patterns and cork and straw bodied mayflies were in use for a century at least, the first straw bodied patterns being listed in 1746, but the effective though these patterns were, the method could only be used for relatively large Ephemera species and it was no good for the smaller Ephemeroptera, which were simply too small to be imitated with the materials available if they had to float.
So it was clear that something else had to be done, but the solution took a long time in coming. A great deal of ingenuity was applied to the problem of making braided silk lines float and all kinds of potions were applied to them, including bacon fat, which must have been interesting, to say the least, if the weather was anything approaching warm. In the end, the tackle manufacturers stepped in and firms like Hardy's and dealers like Chalkley started selling red deer fat, which was rubbed onto silk lines using a cloth.
Needless to say, some anglers objected to the idea of having to carry a stinking cloth dripping with rancid fat around in their pockets in high summer, so before long it was possible to buy special applicators, sealed up in leather cases, containing long pads onto which the fat was rubbed - all that had to be done was to pull the line through the case and it was ready to go. The trouble was that a single application rarely served all day, which is one reason why we ought to appreciate plasticised floating fly lines more that we do - they solve more problems than most people imagine today, including having to explain why you smell strongly of dead deer.
Faced with this sartorial challenge, the tackle manufacturers put their heads together and after much research, more acceptable preparations were developed, mostly based on perfumed petrochemicals. These were far easier to apply than animal fats, lasted longer and weren't nearly so pungent. Very little has ever been written about this backwater of fly fishing history, but preparations like Hardy's Cerolene were real game changers.
The next challenge anglers faced was making their flies float. To some extent this had already been addressed, as recounted above, but cork and straw-bodied mayfly patterns were bulky and hard to handle, even if they did float amazingly well. Remember that all their patterns were tied wth organic materials, which meant that two or three false casts had to be made every time the fly was lifted the fly off the water in order to dry it - even then this only delayed the inevitable and frequent changes of pattern were necessary. This tedious ritual may well be one of the reasons why the late nineteenth century British dry fly men became so fixated on casting to rising fish; they had grown up in an era when in practical terms, there was no other choice. Untreated patterns quickly became waterlogged and if you 'searched the water', you ran the risk of finding yourself in the middle of a fly change at the very moment a good fish rose.
That something was paraffin, better known to American readers as kerosene and it is said that this happy innovation was made by a relative of Colonel Peter Hawker's. Paraffin was in widespread use for treating dry flies by the 1880s, although early adopters had known about it long before, as evidence for which, we can quote Hi-Regan, who recalled his introduction to dry-fly fishing in 1857:
In the 'Mutiny year' paraffin oil was little known, but 'Pegg' made many raids on the bottle of 'Burmese oil' which I used for my guns. This was the 'thinnest' oil then known, and he used it to steep fly materials before tying. These he dried, and although he lost some material by discolouration, he preserved enough for his purposes. Not thinking dry-fly fishing worth pursuing, I took no pains to acquire the niceties of it, and must store away with other regrettable indiscretions of my youth, my neglect in not learning the secret of making feathers 'waterproof' (Pegg's word). In this connection, may not the popularity of coot's, mallard's, teal's, and starling's feathers be accounted for? They are all birds which have oil glands for lubricating their plumage. Rail's feathers also resist moisture, to enable the bird to comfortably traverse the meadows.
To begin with, paraffin was brushed on to flies using bottles like the Bennetfink bottle above and it was particularly helpful where small, less buoyant flies were concerned, although there was always the risk of the stopper coming out of the bottle and leaking the greasy contents all over the owner's clothers. It wasn't an ideal solution for other reasons, largely because it took time for the 'slick' of excess flotant to disperse, and this made quick changes of pattern slightly difficult, but it was far and away the easiest way of getting a fly to float. The other and much trickier problem was that paraffin accentuated the colour of the majority of furs used for bodies. While this baffled anglers for a short while, it was soon overcome and there was a period when it was common to tie dry flies with quill, horsehair and celluloid, materials whose colours were not altered by paraffin and which had the added advantage of not absorbing water.
Some parties thought brushing petroleum derivatives on flies was a bit unsporting and there was much speculation that trout didn't like the flavour of natural paraffin, with the result that a period of experimentation with deodorised paraffin followed, but the fish didn't seem to mind and it was abandoned. A rather tongue-in-cheek Hills recorded some of the arguments against the material in River Keeper
Deep were the doubts expressed and gravely were heads shaken over this dangerous novelty. Would not paraffin prevent the fish from taking? Would it not put them permanently off the feed? Would it not foul the water and poison the fish? And, if none of these disasters happened, would not the cooked trout smell and taste abominably?
Another popular method of treating a fly so that it would float was to dissolve Vaseline in petrol; the artificial was dipped in the solution, and the petrol left to evaporate, leaving the fly coated in the gel. Once this method was perfected, the stage was set for a mini-golden age of dry fly gizmos, designed to paint, spray, or drizzle paraffin onto flies, without the risk of unplanned escapes (paraffin soaked clothes being a serious fire risk in an age when smoking was far more common than it is now). The ingenuity behind the design of some of these devices has to be seen to be believed, although there are one or two which were simply too clever for their own good - and although they were manufactured in quantity, few remain, perhaps because the majority of their owners flung them into the river in disgust. As an example we give you the ferociously complicated Illingworth oiler, most of which survive without their internal mechanisms, which, with few exceptions sprang to freedom long ago.