# What's wrong with this line in a baking recipe book?

A cookie-baking recipe book (this one, specifically) has the following instruction in it, which is incorrect in a single spot:

If you have a fan-assisted oven, you will need to reduce the recipe temperature by 68°F. Fan-assisted ovens all perform differently, so always refer to the manufacturer's instructions.

Can you figure out what's wrong with the instruction just by looking at it, and what correction you need to make? The error is not a simple grammatical error, but it does have to do with language.

I first found this problem here, so I cannot take credit for it. However, the mistake in the sentence does exist independently in a recipe book that I've also cited.

• I'm not sure how this question relates to retrograde-analysis. Isn't retrograde analysis a type of chess puzzle?
– f''
Dec 28 '15 at 8:02
• Something wrong with it (but probably not what you intended) is the transcription error of using the "ring above" character, instead of the degree sign: "˚" vs. "°" :) Dec 28 '15 at 8:40
• @f'' I'm borrowing the chess puzzle term to describe this sort of puzzle where you need to figure out what's wrong with a given situation without being given any information about how anyone got there. If I'd given the 20°C measurement alongside the Fahrenheit, the puzzle would have been pointless.
– user88
Dec 28 '15 at 13:50
• It doesn't really have much "to do with language" imho... Dec 28 '15 at 17:07
• There are MANY problems with these two sentences, as suggested by all the answers. I think it's hard to say which is THE correct answer...
– Tony
Dec 29 '15 at 0:34

The cookbook should have read: "Reduce the recipe temperature by 36°F." (Or perhaps 35 or 40, for a "round" amount—"36" implies an unwarranted degree of precision.)

The original source that the cookbook was based on presumably said "reduce by 20°C." However, Celsius and Fahrenheit are relative scales (with different definitions of zero), not absolute scales. The cookbook authors erroneously did the conversion as if 20°C were a specific temperature, which does correspond to 68°F, but when converting intervals, one should not do the zero point adjustment: a difference of one degree Celsius corresponds to a difference of 1.8 degrees Fahrenheit.

• Actually this seems to be the answer, as strongly hinted in the link given by OP. Dec 28 '15 at 8:57
• The error (and the conversion chart described in the linked puzzle) appears to be common to cookbooks published by Workman Publishing. There, though, as well as in the "Cookies!" book cited by Joe Z., the amount is given as "20°C (68°F)", making the error easier to figure out. Dec 28 '15 at 9:39
• "Can you figure out what's wrong with the instruction just by looking at it" > this doesn't seem to point us to consult the other versions of the recipe, and still it seems it was needed so we could figure out the conversion mistake. Sounds somewhat unfair. Dec 28 '15 at 15:58
• @igorsantos07 FWIW, I didn't look up the error source until after posting this answer, so it is at least possible to figure out without it—Streamcap's "oddly specific" hint was what helped me figure out that it was a conversion mistake. Dec 28 '15 at 18:22
• I would not have known that 68 is an oddly specific temperature to adjust a recipe by, nor that it would be too much to compensate for a different kind of oven. The fact that assuming it was incorrectly converted from Celsius gives a nice round number is Bayesian evidence for this error, but we're I not expecting a clever puzzle solution, wouldn't overcome my priors on the book being converted from Celsius and this mistake being made. A hint that this book was adapted from Europe would help.
– xnor
Dec 28 '15 at 22:26

I've never used a fan-assisted oven before, but sixty-eight degrees seems like a huge change in temperature. Perhaps the intended instruction was to reduce the temperature by six to eight degrees.

A nitpicky answer along the lines of "if they have eggs, get a dozen":

This says that if you have a fan-assisted oven, you need to reduce the temperature. However, you might have multiple ovens and be baking the cookies in the non-fan-assisted one. So to be entirely correct, it should say, "If you are using a fan-assisted oven to bake these cookies..."

The phrase "reduce the recipe temperature" tells me to actually change the figures in the book, rather than simply reducing the temperature setting on the oven. A correct phrasing in this fashion would have been something along the lines of "use the recipe temperature reduced by".

On a side note, the amount "68" seems oddly specific given the context...

• +1: The aside about 68 being "oddly specific" helped me figure out the author's likely error: false precision can be introduced by conversions. Dec 28 '15 at 8:40

If the ovens "all perform differently" to the extent that they need to "refer to the manufacturer's instructions", then recommended temperature reduction should not be expressed as a precise "need".

You should not adjust the temperature of the recipe (assuming it is at safe room temperature) but rather adjust the temperature of the oven.

It should read temperature given in the recipe

• why was this downvoted, given that "recipe temperature", if read like "oven temperature", could viably mean "chill your cookbook"... Dec 28 '15 at 23:11

Pedants' corner:

According to Wikipedia, the symbol for Fahrenheit is - a single symbol, represented, for example, in Unicode by codepoint U+2109.

The text above uses two symbols, ˚ and F.

Of course, I didn't figure this out just by looking at it...

• The article says exactly the opposite. Precomposed forms are typically deprecated. Dec 30 '15 at 2:10
• Ah, but you've fallen into the trap of assuming that I read past the first sentence. Surely you know Wikipedia doesn't work like that. Jan 4 '16 at 8:36

The problem is in reducing the temperature by 68 degrees Fahrenheit. This is 293.15 Kelvins, a huge difference. The Fahrenheit scale zero is a nonzero amount of heat, so even reducing by 0 degrees would be a (large) change. Pragmatically, the sentence means to decrease the Fahrenheit temperature measure by 68.

• A difference of 68 degrees Fahrenheit is a difference of about 38 degrees Celsius. I'm not sure I follow you. Dec 28 '15 at 4:36
• He's noting that "...by 68*F..." is not semantically identical to "...by 68* in F..." Dec 28 '15 at 5:16
• @xnor: You're so close, but so, so far.
– user88
Dec 28 '15 at 5:31
• I think @Fimpellizieri knows the correct answer, though.
– user88
Dec 28 '15 at 5:31
• I don't understand this answer at all. In American English, "reduce x by y" means "subtract y from whatever amount is referred to by x". For example, if the recipe specifies baking at 350°, and then says "reduce the baking temperature by 68°", one would bake at 282° instead. I can't see how Kelvins enter into it at all. More likely the use of the word "recipe" instead of "oven temperature" is the problem. In American English, "reduce by 0°" means no change. Dec 28 '15 at 6:40

Shouldn't it be "recipe's temperature" ?

• This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. - From Review Dec 28 '15 at 13:21
• @AlbertMasclans It's an answer expressed as a rhetorical question. Dec 28 '15 at 13:25
• @Lawrence Exactly what I intented. Thank you for the clarification Dec 29 '15 at 9:24

I know the answer has already been accepted, but I just wanted to point out another issue with the instructions as given that I haven't seen anyone else point out.

It says you should reduce the temperature by 68 degrees Farenheit, which is impossible with most commercially available ovens since they tend to only let you select temperatures in increments of 5 degrees. Now, there may be ovens that allow that precise of a temperature selection, but I've never seen one, which makes this a pretty silly thing to put in a cookbook that seems to be aimed at amateur bakers.

This is my first time here, and sometimes I'm too verbose, so apologies in advance; however, given the statement: "The error is not a simple grammatical error, but it does have to do with language", it appeared to me that Joe Z. was asking to find a more complex grammatical error. As such, I am going for the removal of the word 'all', since the statement implies that each individual oven would perform differently; compared with the same statement without the word 'all', meaning that "ovens-with-fan" perform different than their convection-oven counterparts.

Although for me, it is easy to spot the silly 68°F reference, which is wrong for multiple reasons; I chose specifically not to pick that as the answer to the question, because it is not wrong "having to do with language"! It is wrong because of a) improper calculation, b) implying accuracy, etc. (i.e., grammatically sound, semantically off.)

I will further point out that there is a second language error: one adjusts cooking temperature based on environment, (equipment, altitude, etc.,) not recipe temp.