To get a general and broad understanding of vital wheat gluten (VWG) and how it is used, you might want to take a look at the vital wheat gluten entry in the forum's Pizza Glossary at http://www.pizzamaking.com/pizza_glossary.html#V
. Most of the members of the forum use VWG in the context of pizza dough but it can also be used to make bread dough, where it helps give more volume. It is also used for the applications that Frankie G mentioned.
The instructions to add a certain percent VWG to a flour or a certain number of teaspoons or tablespoons to a cup of flour are very common instructions. However, those instructions are a one-size-fits-all approach that fails to take into account the protein content of the flour to which the VWG is added or the protein content of the final blend. Understandably, VWG producers do not want to give instructions for every conceivable flour to which their VWG might be added. In my opinion, the far better approach to take is to use the Mixed Mass Conversion Calculator at http://foodsim.unclesalmon.com/
. That calculator gives you complete control over all of the numbers and in a way that is far more accurate than following the instructions that producers of VWG give to their customers as to the use of their product.
To use the Mixed Mass Conversion Calculator, you select the base flour that is to be supplemented with VWG, and also the brand of VWG that you plan to use. There are two pull-down menus that contain many common and popular types and brands of flour and VWG. If a particular brand or type of flour or VWG is not in a pull-down menu, you need to know the protein contents of the flour or VWG and then use the substance A field and/or the substance B field, as appropriate. Once you have made these selections, you then decide on the desired weight (target mass) of the final blend of the base flour and the VWG and its desired protein content from a percent standpoint (target percentage). For example, you might want to add VWG to a bread flour, such as the King Arthur bread flour (KABF) with a protein content of 12.7%, to get a final protein content that is the same as a high-gluten flour, such as the King Arthur Sir Lancelot flour (KASL) that has a protein content of 14.2%. The calculator will allocate the target flour weight between the amount of the base flour to use and the amount of the VWG.
There are a few other things I think you should know about VWG. First, just because you add VWG to a particular flour to achieve a protein content of another flour does not yield a product that is the same as the other flour. So, adding VWG to KABF does not give you KASL. Second, not everyone likes the effects produced from using VWG. It is usually a taste thing but it might also be a texture matter. So, you will have to decide for yourself whether you like it or not. Third, if you add a certain amount of VWG to an existing quantity of flour, you may have to adjust the hydration to compensate for the fact that VWG has different absorption characteristics than most flours. Usually, the advice is to increase the amount of water by 1 1/2-2 times the weight of the VWG. Fourth, it is perhaps not a good idea to use VWG to make a protein jump between flours that is too great. Going from all-purpose flour to bread flour or from bread flour to high-gluten flour seems to work pretty well but not going from, say, all-purpose flour to high-gluten flour. Finally, I tend to agree with Frankie G that it perhaps is not the best idea to supplement 00 flour with VWG. It can certainly be done, and I don't like to discourage people from trying things, but I would rather select the proper type or brand of 00 flour with the proper protein content.
I have written extensively on the subject of VWG, so if you would like to read and learn more, you might want to do a forum search using the Google Custom Search feature that you can access at the bottom of the index page of the forum. You might use the keywords "vital wheat gluten" (in quotes) along with my name--Peter--which I use in closing all of my posts. That should take you to my posts where I have discussed VWG.