Thank you Jason but that is not the solution I am looking for . I already have an all smart collection filtered by price. Smart collections allow to "show products with tags " but don’t allow to “exclude products with tags”. The other way around of course would be to make a smart collection tagged “all” and not outlet..;;but..
..What I want is to do is leave “outlet” products visible in my shop but I don’t want them to show up in the "all " collection. Now my template shows all the tags to the customers and that helps them narrow their search. For this reason I can’t create irrelevant tags : tagging “all” wouldn’t work because there is already an automatic all tag ( showing all products); " tagging new or else doesn’t look good on the screen either and it means having to un-tag when I want to make them outlets (there could be hundreds of them!).
For me the simplest way would be to change the liquid code over smart collections (which is not such a bad idea depending on the problem).