Japanese markings on vases are often written in a stylized handwritten script that is difficult to read. Tricks to identifying the writing requires a substantial knowledge of Japanese writing systems, both modern and historic, and familiarity with Japanese calligraphy methods. Knowing the age of the vase may help you determine whether you should look for ancient Japanese writing, which came from China, or more modern syllabaries. Additionally, knowing the type of writing used will help determine whether the words are used phonetically or literally.
Take the vase to an antique dealer or specialist to determine its age. Japan has no native writing system but was introduced to the Chinese writing system in the sixth and seventh centuries. Over time, this writing system was simplified, then further simplified. Modern Japanese uses roughly 2,000 Chinese characters plus two syllabaries of 46 characters each. Knowing the estimated age of the vase will help determine the most likely style of writing to look for.
Scan or photograph the markings on the vase using a high-resolution scanner and avoiding using a flash, if possible. The clearer the images, the better for translation.
Inspect the markings closely in the scanned or photographed images. Often there are long trails from the calligraphy brush that may have implied words or may simply be the artist's style of writing.
Print several copies of the images, if desired, and trace over the calligraphy as you try to get a feel for what was written or implied. If you have no knowledge of Japanese writing systems, it might be best to take the images to a Japanese language professor or historian.
Write down possible characters you recognize from the writings on the vase. Use these characters to search for words in a Kanji (Chinese character) dictionary. Sometimes figuring out the main characters gives the best general interpretation of what the artist wished to convey.
Consult with a Japanese language professor or historian regarding the writing on the vase, if desired. Writing on artwork and pottery may be a famous poem or a poem compiled by the artist. A Japanese language or literature professor is likely to recognize this type of writing and be able explain the meaning and translation.
If the vase has one single character, or a construct of two characters that have a semi-complicated detail (meaning, a lot of brush strokes), it is reasonable to assume the vase is relatively new, as opposed to an antique, and the characters will easily be found in a Kanji dictionary. Look up the single character, or, if it is a construct, look up the first character (on the top if vertical, or on the left if horizontal). Beneath that character in the dictionary you will find the compound containing the second character on the vase.