SPACES & QUADS—BASICS

The basic unit of spacing is the “em”. An em makes a visual space that is a square of a given point size. (See “What It’s All About: Proportional Spacing” and “Em Quad,” below.)
    Physically, a 12-point em space (for instance) is a piece of metal a bit more than three quarters of an inch long, and 12 points on each of the four short sides.
    Spaces are sized in fractions of an em or multiples of an em. (The only notable exceptions are for the very thinnest spaces, made of brass and copper. These are always one point and one-half point thick, respectively.)

A distinction is traditionally drawn between “spaces,” in the strict sense, and “quads.” However, spaces and quads can be referred to collectively as “spaces.” (“Spacing material” would serve as a more rigorous collective or generic term.)
    You don’t have to worry too much about always using the right term. However, the space/quad distinction has a certain rationale (discussed below), and it’s firmly established in typographic usage and literature, so you definitely need to be familiar with it.

Spaces, in the strict sense, are the ones typically used within text: This includes the smaller fractional spaces: 3-to-em, 4-to-em, 5-to-em. Fractional spaces smaller than 5-to-em also exist; they are used mainly for large type.
    “Spaces” also includes brass and copper spaces, which are not fractions of an em: a brass space is always one point thick, a copper always a half point.
    It’s always 3-to-em, 4-to-em, and so on, for spaces. There are three of them (and so on) to an em. If you just say “3-em,” or even “3-em space,” it will make people wonder if you are referring to a quad three ems in width, and clarification will always be required.

Quads are en (= half an em), em, 2-em, and 3-em. The latter two are 2 ems and 3 ems wide, respectively. (“Quad” is a shortened form of “quadrat.”)

It’s handy for communication to be able to make a concise but clearly audible distinction between a 3-to-em space and a 3-em quad.
    One likely reason why printers maintained a distinction between “spaces” and “quads” is that it lets us think, and do arithmetic, in terms of the same simple numbers (2, 3, etc.) both for multiples of an em and for fractions of an em, while allowing for a terminological distinction between multiples of an em and fractions of an em. This is useful for a proportional spacing system (below). But the en quad is a problem for this, since it, too, is a fraction of an em (one half).
    The following may help you remember which are quads: A possible psychological basis for the distinction, and for the term “quad,” is that an en (half a square), em (square) and larger quads are easily thought of in terms of their shape, which is rectangular (quadrate), with simple ratios between the sides, ratios which are easily discerned since the dimensions are larger. Smaller pieces are easier to think of in terms of width—it takes practice to recognize them by shape, especially 4-to-em and smaller spaces.

WHAT IT’S ALL ABOUT: PROPORTIONAL SPACING

The common widths of spaces and quads are described below, with important notes on their use. Farther on are descriptions of some other types of spacing material you may run into occasionally.

SPACES & QUADS—
STANDARD WIDTHS AND THEIR USES

2-EM QUAD

A quad that is two ems wide. Used for spacing out after short lines of type, when there is no room left for 3-em quads. Also used for indenting blocks of type, and for other miscellaneous occasions.

EM QUAD

An em is a square of the body size (the dimension in points measured from top to bottom, usually the same as the nominal point size of a given font). For example, viewed from the top, as in the diagram above, an em at 12-point is a square 12 points on a side. An em at 36-point is a square 36 points on a side.
    The em quad is used as a component of paragraph indents, and in other situations where a consistent proportional space larger than a word space is needed (as in tables, hanging indents). Also for one-off use in filling space at the end of a short line when larger quads are too big.

See also “More About Ems and Ens,” below, for some other questions that come up about the terms and their definitions.

EN QUAD

An en is half an em. Like the em, the en space is used as a component of paragraph indents, and in in other situations where a consistent proportional space larger than a word space is needed (e.g., tables, hanging indents). Also for one-off use in filling space at the end of a short line when larger quads are too big.
    En quads are used occasionally as wide word spaces—for instance, in letterspaced heads, or, in extreme cases, in justified body text.

In many text fonts, both metal and digital, the widths of the figures (numbers) are set uniformly at one en, so as to facilitate setting tabular matter. In such contexts, the width of an en may be referred to as a “figure space.” (OpenType font technology now makes it possible create fonts that allow a choice between tabular and proportional widths for figures.)

See also “More About Ems and Ens,” below, for some other questions that come up about the terms and their definitions.

3-TO-EM SPACE

The typical word space, though it may be too wide for, e.g., condensed faces or large type. Narrower spaces may also be preferable where the word space is preceded or followed by punctuation, or by a letter whose shape leaves much extra visual space next to the word space.
    Also for one-off use in filling space at the end of a short line when quads are too big.

4-TO-EM SPACE

Used as a thinner word space (in tight lines, condensed type, or after punctuation, or before/after letters with open space next to the word space.
    Also for one-off use in filling space at the end of a short line when larger spaces are too big.

5-TO-EM SPACE

Used as a thinner word space, especially after punctuation, or before/after letters with open space next to the word space; probably most appropriate for these uses in tight lines or with condensed type, or in large sizes.
    Also for one-off use in filling space at the end of a short line when larger spaces are too big.

6-TO-EM SPACE (AND SMALLER FRACTIONS OF AN EM)

Probably found only in larger point sizes. In these sizes, and especially in tight lines or with condensed type, might be used as a thinner word space, especially after punctuation, or before/after letters with open space next to word space.
    Also for one-off use in filling space at the end of a short line when larger spaces are too big.
    At small sizes, it is impractical and unnecessary to use fractions of an em smaller than one fifth. A 6-to-em space at 12 points is 2 points thick; at 6 points, it is one point thick, which is the thickness of a brass space regardless of point size.

For fine spacing with large sizes of type, spaces in smaller fractions of an em (e.g., 8-to-em) were also made, as were 2-point lead spaces. One- and two-point leads can also be cut to size for spacing, with care and perhaps some trimming, to ensure that the leads are not bent and there is no burr on the edge, which would make the fit less secure. See also “Spaces & Quads—Other Widths,” below.)

BRASS SPACE (1 point thick)

Handle them with care to avoid bending them. Especially in tight lines, and with copper spaces, the best way will often be to pull out the two spaces or types on either side, sandwich the fine space between them, and replace them all as a unit.
    They should not be used when the same result can be obtained by replacing a previously set space with a slightly larger space. (For example, by replacing a 5-to-em space with a 4-to-em space.)
    You shouldn’t often have to use more than one or two brass or copper spaces in a line.
    Don’t use if bent: bent spaces are like springs, so a line may feel tight enough in the composing stick but won’t be as tight as the other lines when the type is locked up, so letters may fall out or be picked up by inked rollers.
    Copper and brass spaces are still made, using the original ATF equipment, by NA Graphics.
    So far, the earliest reference to copper and brass spaces I’ve found is in A.A. Stewart’s Typesetting (1919). There, and in the 1923 ATF catalog, they are spoken of as something that not every shop will have. I’d always taken them for granted, so this surprised me. But many of the more precise ways of working, and the required hardware, were not feasible until the point system was standardized (1880s–1890s), and then it took a while to see the possibilities and start manufacturing them (and then sort out the ones that weren’t that useful after all). Stewart refers to them as “”copper-thins, and brass-thins.”
    Note that “hair space” and “thin space” usually refer not to copper and brass, but to the thinnest varieties of lead spaces, smaller than 5-to-em but no smaller than two points thick (or, rarely, one point). I’ve sometimes wished for an unambigious generic term for these thinnest spaces in metals other than lead. But I know of none better than “copper and brass spaces,” which is adequate for most occasions but excludes the rarely seen steel ones.

COPPER SPACE (1/2 point thick)

Use as for Brass Spaces, above.

STEEL SPACE (1/4 point thick)

Use as for Brass Spaces, above.
    These were certainly not as common as the copper and brass spaces. I know of them only because a couple of people mentioned them in a Briar Press discussion thread. I have yet to find mention of them in any catalogs or other literature. They would be very handy things to have around for fine work.

SPACES & QUADS—OTHER WIDTHS

“THICK SPACE,” “MID(DLE) SPACE,” “THIN SPACE,” “HAIR SPACE”

These terms show up frequently in old metal type literature. They’re also found, if you look, in digital type, in InDesign and Unicode. However, their exact meaning is usually problematic, and the terms should therefore be avoided (except for technical font work involving Unicode). In general, it’s best to think and speak of spaces in terms of fractions/multiples of an em, or, for the narrower spaces in digital type, in terms of “units” (below).
    Moxon (1683) mentions thick and thin spaces, but does not, as I recall, give sizes for them, though on p. 99 (Typothetae ed.), in a discussion of forging punches, he seems to imply that a thick space is one quarter of an em.
    Johnson, in Typographia (1824), vol. II, p. 66, writes that thick spaces are 3-to-em, middle spaces 4-to-em, and thin spaces 5-to-em, while the hair space is finer than any of these, “cast remarkably thin.”
    Southward, in Practical Printing (1884), p. 8, writes: “Spaces are of four kinds, and called respectively, thick, middle, thin, and hair spaces.” He states that thick spaces are 3-to-em, middle spaces 4-to-em, and thin spaces 5-to-em. “The hair spaces,” he says, “average eight to the em, but range between seven and ten, according to the size of the body.”
    A.A. Stewart, in Typesetting (1919) writes: “The thickness of hair spaces varies according to the size of the type; the name is given generally to any cast space thinner than the 5-to-em.” (Note that “cast spaces” excludes copper and brass spaces, which were cut from strips. Stewart treats these separately.)
    Thus, at least for the 19th and early 20th century, you might take the following as rules of thumb for the meanings: Thick space, 3-to-em; middle (or “mid”) space, 4-to-em; thin space, 5-to-em; hair space, anything smaller than 5-to-em.
    However, the 1907 Barnhart Bros. & Spindler catalog refers to copper & brass spaces as “thin spaces.” Stewart (Typesetting) refers to them as “copper-thins, and brass-thins.”

For hair spaces and thin spaces (and other special spaces) in InDesign and Unicode, see the article Special Spaces in Unicode and InDesign in the Digital section of this site.

QUOTATIONS (“QUOTATION QUADS”)

Quotations are intermediate in size and function between quads and metal furniture. Typically, they are partly hollowed at bottom and/or top. In shops that use them, they are stored separately from spaces, since they are not needed for every job. Special cabinets were made for them. Quotations don’t necessarily have to match the size of any type being set, since they would often be used for spacing btween sections of type.
    Quotations are used to avoid the use of large numbers of smaller quads—this saves time and reduces the danger of pieing type. They are more accurate and give a solider lockup than wood. They are also lighter than solid quads and slugs, more space-flexible than larger furniture, and more accurate than wood furniture.
    Quotations are fairly often referred to in the literature. Southward, in Practical Printing (1884), p. 60, writes: “Quotations are large hollow quadrats, and used sometimes in the place of metal furniture. They appear to have been at first used to justify side-notes or quotations in book work, and were called ‘quotation quadrats.’ This use has long since passed away, and they are now simply hollow quadrats, used for filing up considerable spaces at the beginning and ends of chapters in book work, and also in job work. Formerly, they were cast to two sizes, broad (4 em) and narrow (3 em).” In his time, says Southward, quotations ranged in size from 18-point 2-, 3-, and 4-em, to “four-line pica 4 x 6 em” (which I take to mean 48-point 6-em, or possibly 96-point 3-em). The range includes 1.5- and 2.5-em quads in some sizes.
    Southward also notes, on p. 8, that “In founts of large type quotations are also included.”
    I have also seen odd-sized quads, in large display sizes, that were cast in quantity on a Monotype machine. Their dimensions (in points) included 60 x 24, 60 x 36, 48 x 36, 72 x 48, and 72 x 60.

PATENT SPACE

A.A. Stewart, in The Printer’s Dictionary, 1912, has the following: “Patent Space—Type spaces of the thickness of two five-to-em spaces; thicker than the three-to-em and thinner than the en-quad. This space is common in 12-point and larger sizes, but the name is not now often employed.”
    I haven’t seen this mentioned anywhere else, and am not clear on how such spaces would be useful. Perhaps it was one of those technical innovations, like “self-justifying” hand type, that didn’t last for long.

2-PT. LEAD SPACE

It’s actually not that unusual for these to turn up, especially in display sizes. You can still buy them from NA Graphics in sizes 12-point and up. They are cut from two-point leading, not cast, and so had no nicks. But they were specially manufactured, so they are neater, more regular, and more accurate than pieces cut on a slug cutter. I have also seen cast two-point spaces, with nicks.

1-PT. LEAD SPACES

You may occasionally see these. They were made on a Monotype Super Caster machine, using an attachment that cut them from strips of 1-point leading cast by the machine. They therefore had no nicks. They are less common than 2-point lead spaces, since they can only be fragile, less accurate, and less durable substitutes for the common 1-point brass space. It is possible that they were made before brass spaces became common, after which they were less generally made and used.

PAPER SPACES

I’ve seen these fairly often in old type cases at MCBA. I’ve never heard or read much about their use. They’re bits of paper cut very accurately to the size of a copper space. At least some of those I’ve seen are no thinner than a copper space. Copper and brass spaces, as far as I can tell, didn’t come into use, or at least weren’t widespread, until the 1920s. I’d guess that paper spaces had been mainly used before that time, and were gradually superseded by copper and brass.
    A.A. Stewart, in Typesetting (1919) writes: “When metal thin spaces [he means copper, brass, or lead “hair spaces”] are not at hand it may be necessary to resort to pieces of paper or thin card. Spaces of this kind should be used only in exceptional cases and not at all as a common practice. There should be never more than a few pieces of paper used in justifying a line. A safe rule for the apprentice, when he thinks he cannot make his line come right without some such expedient, is to ask an experienced compositor, who will usually show him how to justify without the paper.”

OTHER SPACING TERMS

UNIT

The term “unit,” as a measure of space or width, is important for both digital type and Monotype hot-metal type. A unit is always a fraction of an em. Which fraction of an em depends on the particular technology, or the particular software, you are using.
    The unit is not a fixed value in any system; its value is relative to the value of an em at whatever point size you are using at the moment. In other words, the unit is a relative measure, not an absolute one. It is relative to the point size, which determines the value of an em. For any given unit system you can find the value of a unit in points, at a given point size, with the following formula: point size divided by the number of units in an em.
    The Monotype Composition Caster used a unit of one eighteenth of an em. Every character and every space the machine cast was a whole number of units in width. This made it easy for the machine to justify lines to exactly even widths, by calculating the number of units in the measure, the number of units taken up by the characters, and the number of units that had to be filled up by each of the spaces in the line. Spaces were cast to the required number of units, disregarding standard space sizes. (See “Odd Monotype Spaces,” above.) (I don’t know if all the different varieties of Monotype machines used the same unit, or if any of them could cut things finer than an eighteenth. What I’ve seen so far, when I’ve looked that closely, suggests that the Composition Casters always used 18ths, and went no finer. Thus, 4-to-em or 5-to-em spaces at a given size might not be the exact fraction of an em that foundry casting could produce.)
    Eighteen was a magic number for typography in the twentieth century. A system based on eighteen, or one of its multiples, yields mainly numbers that are divisible by two or three, or by their multiples. I would guess that it was this that made it feasible to build an analog computer—that is, a mechanical computer like the Monotype Composition Caster system—that would function for setting type.
    Perhaps more importantly, a base-18 system made it easier to do the needed calculations with a proportion wheel, a hand calculator, or in your head. Some of us did such calculations very, very frequently. (In the 80s, I had a table of unit values for 54ths of an em on a pencil holder on my desk.)

For more about units in digital typography, see the article “Units”: A Fundamental Measure of Space And Width.

MORE ABOUT EMS AND ENS

Em/En auditory confusion, and terms meant to avoid it

“Em” and “en” sound very much alike. People who worked with metal type all day every day soon learned their way around this, but there was never, as far as I can tell, an elegant linguistic solution to the problem. What worked for the people who worked together in a given shop was all that was needed.
    In practice, when you refer, in speech, to an em or an en, you always have to enunciate very, very clearly to distinguish eM from eN.
    Among metal type people, an em was sometimes called a “mutton,” to audibly distinguish the name from “en.” This works.
    However, some people carried the idea too far, shortening “mutton” to “mutt.” This defeats the purpose, since “mutt” sounds as much like the more common word “nut” as “em” sounds like “en.“ I have even heard people who should have known better refer to an eM space as a “mutt,” and an eN space as a “nut,” which brings back all the original confusion.

TELLING THEM APART

KEEPING THEM IN ORDER IN YOUR SHOP

WORKING WITH SPACES AND QUADS

How tight to make the line?

Each line should be set so the type is tight enough that it won’t fall forward if the composing stick is tilted. (Make this test with a lead or slug in front of the line.) You shouldn’t be bending spaces while trying to jam them into the line: if you are, that probably means that you should use a slightly smaller space somewhere else (e.g., a 5-to-em space instead of a 4-to-em space). Ideally, all lines should be equally tight, so they compress equally when the type is locked up.

Filling out a short line (e.g., paragraph end):

For this, it’s simple to apply the principle of as few spaces as possible, as large as possible.
    For example, when adding spaces to fill out a short line, insert 3-em quads until no more will fit, then use the next size that will fit (no more than one will usually be necessary), and then the next size that fits, and so on until the line is justified.
    Put the largest quad/space at the end of the line, up against the right side of the composing stick. Then put another quad/space of that size, or the next largest size that fits, up against the type. This prevents type from falling while you are spacing out the line, and prevents small spaces from falling out at the end of the line.
    Keep the smallest spaces all together in one spot. (Or use one or two larger spaces—perhaps en spaces—to separate two groups of the smallest spaces, if that makes it easier to insert spaces, especially coppers and brasses, without bending them.) This simplifies distribution. I like to put the small spaces close to the type (with the one big space between them and the type), so the big spaces that can stand on their own are toward the outside of the line where the danger of spilling is greatest.
    Here is a depiction of a short line of type with spaces added to fill the measure, by the method described above. The spaces, from the left, are: 3-em quad, 5-to-em space, brass space, copper space, en space, 2-em quad, two 3-em quads.

(Screen resolution doesn’t do this justice.
Take my word for the copper space.)

Justifying a full line of text:

“Justifying” type means spacing it out so that the words fill the full width of the column, creating even margins at both sides.
    In full lines of justified type, when adjusting spacing to justify a line, keep the word spacing as consistent as possible throughout the line. Uneven word spacing within a line is highly visible in print. Techniques for spacing are detailed below—first for adding space, then for reducing space.
    Once again, use as few spaces as possible to fill a given area. For example, instead of adding a copper space after a 4-to-em space, try replacing the 4-to-em space with a 3-to-em space.

Adding word space to justify:

Adding word space to justify a line should be done by replacing existing word spaces with slightly larger ones, not by inserting brass or copper spaces. Start with spots where word space can be added with little visual impact: the spots where the largest sections of letters directly abut the word space. Examples are full-height verticals, such as ‘d b’. Then add space where, e.g., half-height verticals abut the word space, such as ‘h m’. The third-to-last spots to add space are where rounds abut the word space, e.g., ‘o c’. The second-to-last is where slants abut the space: ‘y W’. Only as a last resort should space be added where a small punctuation mark, like a period, comma, or quotation mark, abuts the word space.
    When all these options are used up, add space as evenly as possible at all the word spaces. The maximum space will depend on the typeface, size, and leading, but anything larger than an en space is too much—except for short measures, where occasional wide spacing is an unavoidable tradeoff. Too much space is worse than too little, but spacing so tightly that words are not easily distinguished is unacceptable.
    Letterspacing with copper, or even brass spaces is also a last resort, but if used carefully and very sparingly, it can gain a small amount of space, which is sometimes enough to prevent having to reset previous lines. Follow the same principles as for increasing word space: add spaces first before large punctuation (such as colons, semicolons, or exclamation points), then between full-height lower-case verticals. There should always (except in very narrow measures) be a better solution than adding letterspace in more than a few spots in a line where the characters come close together. (Even in very narrow measure, major letterspacing should only be resorted to when resetting and re-spacing will not help.)
    If necessary, a good typographer will go back and respace earlier lines as needed to bring up or push down a word or part of a word in order to justify a problem line without excessively tight or loose spacing.

Tightening word space to justify:

When tightening word space to justify a line, proceed in the opposite sequence as for adding space: start by reducing word spaces that abut punctuation, then those that abut slants, and so on.
    Never remove all the physical space between words, no matter how open the shape of the letters before and after the word space.There should be at least one sixth of an em space.That’s a brass space in 6-point type, and more in display sizes (over 14-point).This is true even if, for instance, there is a period before the space and a capital T after.The eye and brain need an unambiguous break in order to recognize a word space without stopping to interpret, so there has to be some definite clearance on a vertical axis between the right extreme of the character preceding the space and the left extreme of the character following, no matter how much white space there is elsewhere on either side of the space.

Removing all the horizontal space between open characters is a mistake that designers sometimes make, when they have little real knowledge, don’t read much print themselves, think that chance-met scraps of information are enough to make them experts, and happen to have run into some discussion of visual word spacing by someone who knows no more then they do. The quirk may even be built into digital typefaces designed by type designers who know less than they think they do.
    You can get away with this in “artistic” pieces, where no-one will read the text if it is of any length, and those who notice will either believe that it must be alright because it is “artistic,” or think that anyone who makes such a mistake isn’t worth wasting breath on to criticize.
    But if you do this in high-end commercial work of any kind, you will soon be faced with clients who insist that the mistake be corrected. I’ve seen this happen regularly in advertising and corporate communications work. It will be even more obvious in book work. Those clients will be right, and they will get their way because it’s easy to find another typographer: the kind of “typographer” who leaves out word spaces is a dime a dozen.
    When something looks wrong enough to enough people to regularly generate complaints from people who aren’t out to prove that that they are typographers, and who aren’t echoing some passing fad of pseudogrammar, that’s a pretty good indicator of bad typography.

Other common spacing issues:

Word spacing will also have to be adjusted to avoid widows, orphans, bad word breaks, ladders, rivers, and unsupported short words.
    A widow is a line containing only a short string of letters, left over at the end of a paragraph. An orphan is a widow on the top line of a page. Widows and orphans must be avoided at all costs. Typography is cruel.
    A ladder is a column of hyphens (or similarly small characters, such as small punctuation) at successive line ends. A river is a group of word spaces at roughly the same horizontal position in successive lines, forming a visible pattern that is noticed by the reader. An unsupported word is a word of one to three letters at the end of the second-to-last line of a paragraph that looks like it’s about to fall into the blank space below.
    An ounce of prevention is worth a pound of cure. It is possible, with practice, to learn to anticipate, to some useful extent, all of these problems, allowing you to adjust spacing as you’re setting a line to avoid go to avoid trouble at the line end.
    You should also monitor your work as you go. In addition to proofreading each line before you justify it, keep an eye out for developing ladders and rivers, and look at how much copy is left in the paragraph to see if a widow is a possibility. Also look ahead for problems such as longish words that can’t be broken at a line end, like ‘through,’ or ‘strangely’ (two-letter breaks are forbidden), ‘cocktail’ or ‘arsenal.’ Or your client’s name.
    Learning to see the best spots to tighten or add space, and the best opportunities to gain or lose words in another line to help justify a problem line, is also essential for good work in digital typesetting. The only difference is that it’s a whole lot easier to make these adjustments with digital type.

Other points about spacing:

There are cases in which legibility will be improved by inserting a copper space may be inserted between punctuation and words. Where this is the case, the extra space won’t be noticed by the reader. (Conversely, if the reader will notice, then it isn’t needed and would be a fault.) Examples are: on either side of an en- or em- dash (especially where a dash is next to a round, since both characters print right up to the edge of the type at about the same height), before a colon or semicolon, or between a quote mark and a capital letter that fills the full width at the top, like a W or Y. Copper (or even brass) spaces may also be used in in such places to add space when justifying a line.
    In some languages, editorial style calls for narrow spaces around punctuation in certain situations. Readers in those languages expect this. English does not use spaces around punctuation in this way. It is a mistake to violate common typographic practices in any language.

STORAGE