I once read an article that included this statement:
"As odd as it may sound, the best way to ensure you lost nothing in translation is to translate the whole thing back to the original language."
I disagree, and here's why.
The underlying assumption of the statement seems to be that translation is a black box with mysterious workings. To discover what problems might be caused by the first black box, a client can run the results through a second black box and compare them.
At its best a backtranslation can be used as an educational tool, to inform the client about the bad impression made by the poor translation they paid for the first time. It has its place as part of a thorough review of translations used in cross-cultural marketing.
But as a translator for over 17 years, I no longer participate in them without discussing them with my client and asking why they are needed. And most of the time they're useless.
Once, a customer had paid someone else to translate a brochure for
one of their products from English into Spanish. They later asked
me to provide an English backtranslation of it.
I was not given the English source brochure. However, on a hunch, I searched online, and found an English version - at their web site.
Most of the Spanish translation was just fine, although the
translator had misunderstood a few passages. I translated them
into English as they were written in Spanish. What I really should have
done was to highlight those items, explain what the translator had
written and what he/she should have used. However, I was not asked to
do that.
The translator was also a little bit inconsistent in his/her use of acronyms and abbreviations taken from the English document. Some had been translated, while others were left in English. In my opinion, they did not reflect well on the company or its product. Since I was only being asked to backtranslate the customer would not be aware of the inconsistencies in the Spanish version.
The rest of the English backtranslation was absolutely pointless. The client didn't need another English version - They had written the original, which was posted at their own web site! I could either copy the English directly from there, and save time; or I could translate it again. Then someone else would have to compare mine to the "official" English version, find the differences, and explain to the client why most of the differences were unimportant.
In my opinion, my client would be better served if I had simply given a detailed opinion about the quality of the translation than by my translation of all eight pages.