I recently had the pleasure of chatting with Jonathan Bernstein of Bernstein & Banleys, one of the few remaining independent trimmings merchants left in the trade. I was interested in meeting for a simple reason. Although I had found a French source for silk facings used in dinner jackets and formalwear, I had not yet found a source for the old-fashioned silk trouser braid used in formal trousers.
I inquired with at least half a dozen trimmings and fabric merchants in NYC but to no avail. I did manage to locate a source for regular silk cord (Botani Trimmings). However, with no sign of the old fashioned trouser braid (see third braid from top in photo below), I feared it was no longer being made.
As it turns out, that fear was altogether premature. Jonathan confirmed that the English mill that used to make this quintessential trimming is no longer in business (and undoubtedly supplied much of Savile Row). But the good news is that after some investigation B&B identified an Italian mill who is able to produce an equivalent braid with similar specifications to the English-made variety.
You might be wondering why I'm putting so much stock in sourcing and understanding the provenance of a trimming a mere 5/8 inch in width? You might also point out that trouser braid is perhaps one percent of the bill of materials for a bespoke dinner jacket and trousers. My reason (or conceit) is fairly simple - modern men's formalwear was originally an English invention.
At least for me, it's heartening to see an active UK manufacture and trade around a dress code that is quintessentially English. Today, of course, quality textile and fabric merchants live in a multi-sourced commercial environment and work with a spectrum of Italian and English suppliers. But from the standpoint of "heritage aesthetics", I like the fact that B&B currently work with a factory in East Anglia for their silk facings. The factory is located in a town whose history with textile manufacture dates back to the Middle Ages.
But set aside the aesthetics of authenticity for a moment. Based on what I saw, I think B&B has the widest and most complete offering of formalwear trimmings in the market. Specifically, I'm speaking about their new silk facings and linings books which offers both traditional options (check out their viscose rayon or ermazine linings) and new trends such as digital print silk linings.
If you're a tailor or designer, I'd encourage you to inquire into B&B (no minimums) and they have a NY-based agent to facilitate orders.