Shipton Mill Organic Strong White #4:

Is a blended flour, produced primarily for Marris Widgeon (a heritage wheat from the south of England where Shipton Mill are located) and continental wheat.  This blending, which is a role carried out by their master millers, gives a consistency in flour quality year after year.
The flour is delivered from Shipton Mill in branded sacks without the words “strong” or “plain” on them but its qualities are identifiable by the use of “12%” printed on the side. This refers to 12% naturally occurring protein in the wheat.
With a protein content of 12% this flour is perfect for sourdoughs, yeasted and enriched breads

This flour is roller milled. Through the process of roller milling the bran and germ are stripped off the grain to leave just the endosperm. The endosperm is then milled to produce a fine white flour.
The endosperm is the part of the grain where most of the protein, starches and sugars are. Gluten being produced from these proteins is mainly found here.  This is the reason why breads made from white flour produce light sweet loaves. 
By removing the bran and the germ from the grain, we also remove most of the trace elements, minerals and nutrients from the flour, as well as much of the flavour. This is one of the reasons I always recommend blending wholemeal flour; be it wheat, spelt, emmer or rye into strong white flour.
Shipton Mill Organic Strong White #4 flour is perfect for such blends, allowing you the baker to create loaves of your own creative choice.

I find a hydration of approximately 70% about optimum for hearth loaves made with this flour.  With the addition of wholemeal flours, the hydration can be increased. Add about 1% extra water for every 10% extra wholemeal flour in the recipe.

The Common Loaf Sourdough Recipe which you can find here, was created from blending 83% Shipton Mill Strong White #4 and 17% Organic Wholemeal Rye flour. It has a hydration of 72%.

If on occasion you would like to make a loaf using all white flour, I find blending approximately 10-15% Shipton Mill Organic Plain Flour with Shipton Mill Organic Strong White Flour gives a loaf with good volume but also has a crust and crumb soft enough to easily bite through.