Practically anyone who becomes seriously involved in studying any aspect of the California missions will eventually come up against the necessity of consulting original Spanish documents of which only a few have been translated. Researchers come to the task with varying degrees of preparation, from native speakers or those who have studied Spanish for many years to those who are totally innocent of the language and hope to attempt translation simply by using a bilingual dictionary. That is foolhardy at best, but there are obstacles that can catch the unwary even if they are fluent in modern day Spanish. Deciphering the handwriting can be difficult for anyone and there is no short-cut. What is required is perseverance and close study until one learns how the author forms each of the letters of the Spanish alphabet.

Spelling is another problem: Spanish is a phonetic language, but sometimes several letters sound the same and the writers of the documents were not always consistent--even on the same page! However, one can give a few hints which should help. As in modern Spanish, "b" and "v" are interchangeable. "C", followed by "e" or "i", and "s" and "z" are interchangeable (the Castillian pronunciation of "c" or "z" as "th" appears not to have been current in early California). "G", followed by "e" or "i", and "j" and "x" are interchangeable and all had the sound of "h". Double "1" and "y" are interchangeable. A final "i" can take the place of a final "y". A capital "Y", followed by a consonant, is actually a capital "I"; followed by a vowel, it is a "y". If any word using any of these letters cannot be found in a dictionary, try substituting one of the other letters of equivalent sound.

Of course, there are simple misspellings as well as transpositions of syllables and these can cause problems. Another difficulty comes from the frequent use of abbreviations; these simply must be learned with practice. Once one has deciphered the handwriting and straightened out the spelling, one comes to the question of what the words really mean. Even for someone fluent in modern Spanish, this can be a problem. Words change their meanings over the years and often the meaning in one region is not the same as in another. Also, there are technical words that can cause the greatest of problems. Often more than one dictionary must be consulted and some words may never be found, though those are relatively few.

One firm rule about translation: if it doesn't make sense, it's probably wrong. Perhaps the words have been mistranscribed or the wrong meaning has been chosen. There could be an error in the original, but that is less likely than an error on the part of the translator.