Under the Brennholt Institute of Applied Taxonomy's survey, bread clips are sold in five common widths, from 28 mm (1.10 in) to 52 mm (2.05 in), and the 38 mm (1.50 in) clip is the most frequent in the retail listings. The Institute proposes classes B1 to B5 for these widths, and records the width of the slot, which is the opening that grips the bag neck, as a separate figure.
A bread clip, also called a bread tag or bag closer, is a small piece of moulded plastic, flat and roughly rectangular, with a tapered slot into which the neck of a bag is drawn. It is made in the billions and sold in bags of one hundred to several thousand, mostly to bakeries and packers. The pack states a count and a colour. It almost never states a width in millimetres, and never a class.
| Common name | Width (mm) | Width (in) | Slot width (mm) | Thickness (mm) | Institute class |
|---|---|---|---|---|---|
| Narrow | 28 | 1.10 | 3.5 | 1.2 | B1 |
| Slim | 33 | 1.30 | 4.0 | 1.4 | B2 |
| Standard | 38 | 1.50 | 4.5 | 1.5 | B3 |
| Wide | 45 | 1.77 | 5.5 | 1.7 | B4 |
| Extra wide | 52 | 2.05 | 6.5 | 2.0 | B5 |
Inch figures are the millimetre value divided by 25.4, rounded to two decimal places. The widths are the Institute's survey means, read across the longest side of the clip. The slot width is the opening at its widest, and the gripping width is the narrow end, where the bag neck is held. The thickness is the plastic of the body, measured away from the rim.
The Institute does not invent where a real rule exists, and here none has been found. The bread clip is made to suit the neck of the bag, and the bag is made to suit the loaf. No standard sets the width of the clip, the shape of the slot or the thickness of the plastic. The one related fact that is published is that most bread bags are made of polyethylene film between 0.02 mm and 0.04 mm thick, and the clip is moulded to grip film of that range.
The clip therefore follows the bag by custom. A buyer who needs a clip for a wide neck, such as a bag for a long loaf, will find that the neck width decides the class, and the loaf does not.
The method is to lay the clip flat on a table, to read the overall width with calipers across the longest side, and to read the slot with the calipers opened inside it. The thickness is read at three points and the mean is taken. The Institute reports the width to the nearest half millimetre and the thickness to the nearest tenth.
The slot is measured with the clip empty and unflexed. A clip that has been used to close a bag is not measured, since the slot opens by up to 0.5 mm after repeated use, and the Institute found that reused clips are often marked by the film.
The common clip is of polystyrene or polypropylene. A clip of class B3 weighs about 0.6 g, and a clip of class B5 about 1.4 g. The Institute weighed a bag of one thousand B3 clips at about 640 g, including the bag. The weight is indicative and varies with the resin and the colour.
The colour of a clip is often used by bakeries to mark the day of baking, and the Institute notes that the colour carries no meaning of size. A bakery may use five colours for five days of the week, and all five are usually the same width.
The classes are the Institute's own, introduced on this page. No maker or packer uses them.
A class says how wide the clip is. It does not say how thick a bag it can close, since that depends on the slot and the plastic. The Institute records the slot separately and does not infer it from the class.
The Institute's survey of retail listings found that bread clips are described by colour and count in more than nine listings in ten. About one in eight gave a width, and when it did, the figure was the overall width and not the slot. A listing that gives the slot is more useful to a buyer, since the slot is the part that grips, and the Institute treats the slot as the primary figure for anyone who is choosing a clip for a particular bag.
Packs are sold in counts of 100, 250, 500 and 1,000. A reader can check a pack against a kitchen scale, with an allowance of 3 per cent.
The bread clip belongs with the twist tie and the hair tie as a small closure for a bag or a bundle, and is catalogued in the department of length and fit. Compare twist tie gauge, which closes the same bag by a different principle, and hair tie sizes, which the Institute treats on the same footing.
The review panel divides on whether the bread clip is a fastener at all. Two members hold that it is a closure, since it holds nothing together and only keeps a neck from opening. The majority hold that a fastener is defined by what it resists, and that the clip resists the opening of a bag as a staple resists the separation of paper. The page therefore catalogues the clip with the fasteners, and the dissent is recorded.
The Institute has not measured the metal-cored closures sold on rolls for automatic bagging machines, which are applied by a machine and not by hand. Nor has it measured clips with a printed or embossed face, whose edges may differ from the plain form. Both are queued for a later survey, and no figure for them appears on this page.
Under the Brennholt Institute's tables, the most frequent bread clip is 38 mm (1.50 in) wide, class B3. Common widths run from 28 mm (1.10 in) to 52 mm (2.05 in).
A class B3 clip weighs about 0.6 g in the Institute's survey, and a class B5 clip about 1.4 g. A bag of one thousand B3 clips weighs about 640 g.
The common bread clip is moulded from polystyrene or polypropylene. The Institute records the resin wherever the maker states it.
No published standard has been found. The clip is made to suit the neck of the bag by custom. The classes B1 to B5 are the Institute's own proposal.
In the Institute's survey the colour carries no meaning of size. Some bakeries use colours to mark the day of baking, and all the colours are usually the same width.