Brush Drawing (or Wire Drawing) was a way of "sticking" bristles to a brush-stock by using hot pitch. This method was used up till the beginning of the 20th century for brooms and household brushes. It was known as "pan-work" as it entailed using a pan of hot pitch.
However, this was no good for making small personal brushes as the pitch would get in your hair. Pitch was also very limited in its water resistant qualities when used with hot soapy water etc. so the way around this was "drawing", and this was the firstaspect of the craft a brushmaker's apprentice would be taught.
In drawing, a wooden brush back is made and holes drilled though it to take the knots of bristle. This part of the brush would usually be the part that included the wooden handle. The holes were each drilled with two bits, one wider than the other so that half of the hole was of a larger bore. A length of wire or thin twine was then passed in loops through the holes from the back of the brush. A small bundle of bristles, about two inches or so long was then pushed through each loop, so that as the loop was pulled from behind the brush back the bristles folded over into the wider part of the hole and were held tight as the wire or twine was pulled. If the brush was for hair the bristles would be left slightly uneven. If it was for clothes, etc. they would be fixed so they would all be even.
After a row of bristles had been inserted the wire was tied off so that they were held tight, and this was continued until the whole brush was "filled" with bristles.
To hand-draw a good hairbrush would be a day's work! After all the bristles were inserted and the wire or twine secured a brush-back of thin veneer would be fixed over it to hide the work. These were glued with fish glue, but as this was also unreliable four small brass screws were also added to keep the back secure. The brush was then "finished"- i.e. shaped, sanded, stained and polished. This could be a specialist job and some brushmakers described themselves as "brush finishers". Brushes are still made this way today, but they are quite expensive and are usually bought by the "upper classes" or those with an eye for quality. The sign of a top quality brush is still the four small brass screws to be found in its back...
