Infosearch (a.k.a. Encore) will not allow you to do a blank search. You have to type something into the box before you can narrow your results by language. Even still, this post-search language limit is not perfect and also does not rule out translations.
I have talked to Jo and Beverly about this. Apparently both versions of our catalog are using the 041 MARC field to determine the language, but should instead be using the 008 field. ?? Jo has sent a request to Ann F. to sort out how we can do a true "language limit" using the 008 field of the MARC record. Stay tuned...
Also, another problem is that only some languages are available as limits in the OPAC. There are no options for Japanese, Hebrew, etc. Jo has also requested that Ann reconfigure the Advanced Catalog Search's language limit to include all of the languages in our catalog as available limit options.
In the meantime, should you find yourself needing to find some introductory readings in a foreign language, here's an another strategy. I accidentally stumbled upon a subject heading for Japanese Language -- Reader that seemed to satisfy my patron.
ありがとう,
Jason