"Rubber-Safe," or "Rubber Safe?"

When advertising a product as safe to use on rubber should a hyphen be included between the words "rubber" and "safe?" It seems to me that because it is a compound adjective a hyphen should be used, but analogous usages such as "dishwasher safe" seem to be infrequently hyphenated. Is this one of those situations where the choice is purely preferential?

The product is a chemical compound that will likely be used in environments where rubber is present.

Solution 1:

It is evident from various comments and general usage that opinions differ on the necessity of hyphens when a noun is being used as an adjective or adverb. In the absence of violation of any grammatical principles, I therefore suggest one makes ones own judgment on style in these cases.

On what criteria should one make such a judgment? The purpose of writing, whether a literary article, a scientific paper or advertising material, is to communicate ideas, and anything that makes reading more difficult or one’s meaning less clear is an impediment to that communication. I therefore suggest that the criteria one should apply are not popularity or modernity, but clarity and comprehensibility.

The general problem here — to which a hyphen can be the solution — is called false scent: as one reads a phrase word by word, it is easy to misinterpret the meaning of the word in the phrase, and this is only corrected on reading further, requiring a mental adjustment, slowing comprehension.

The extent of the ambiguity depends on the context in which the pair of words are used, and to some extent on the actual words, so I shall consider some different contexts. I shall refer to the combination of the two words (here ‘rubber’ and ‘safe’) as a compound for convenience and to be without prejudice to their parts of speech.

A. Attributive adjectival use of ‘compound’

e.g.

1. Super Wizzo is a rubber safe product

v.

2. Super Wizzo is a rubber-safe product

Reading 1 up to the first italicized word one can receive an initial impression that either SW is a condom (US) or an eraser (UK). Reading the next word suggests that it is an adjective describing ‘safe’ — a security box — perhaps a safe made of rubber or one for storing condoms or erasers. Only finally is it evident that the two words are a compound adjective describing ‘product’. In 2, the hyphenation of ‘rubber’ and ‘safe’ make it clear that they constitute a compound adjective. It seems to me that the hyphenated form is the obvious choice if one wishes ease of reading.

Even if the initial noun is generally non-countable like rust (e.g. rust + proof) or air (air + tight) then

Super Wizzo is a rust-proof product

eliminates the initial puzzlement on encountering ‘a rust’ in

Super Wizzo is a rust proof product

Likewise for ‘air-tight’.

B. Predicative adjectival use of ‘compound’

For example:

1. Super Wizzo is rubber safe

v.

2. Super Wizzo is rubber-safe

Although the compound stands alone, in 1 one can still get false scent from reading the first four words “Super Wizzo is rubber” (made of rubber?) which the hyphen in 2 avoids.

C. Compound standing alone

The simplest situation is the compound standing alone, perhaps as labelling on the side of the box of Super Wizzo — Rubber safe or Rubber-safe. If the front of the box has a picture of Supper Wizzo and it is clear that it is cleaning product (or whatever) rather than a safe, then the false scent in the form without the hyphen is minimal (especially if it is followed by the inevitable exclamation mark).

Here you can leave out the hyphen if you think it looks cleaner, or stick with it because you’ve come to love hyphens.

Footnote

1. Like @MarkHubbard I think “safe to use on rubber” is clearer than “rubber-safe”. But that wasn’t the question, and in advertising words are at a premium.

2. These remarks apply also to “dishwasher-safe”, whether or not it is seldom hyphenated in practice. The ambiguity may be less, but is still present in A and B. One has to apply criteria and make one’s own judgment.