There are few more controversial subjects in bonsai than the use of deadwood in bonsai design. More than any other it seems to polarise opinion , those who see no place for it and others that perhaps use it to excess.
This is intended to be a discussion on it's use rather than a treatise on how to do it and what tools to use , so lets look at the reasons why the use of deadwood might be appropriate. To do this I think it may be good idea to look at what are the basic objectives in the creation of bonsai.
The way I see it there are two main aims when creating and developing trees into bonsai. The first is to make our small tree in a pot appear to be larger , much larger than it is , the miniaturisation element of the art. The second is to give our tree the greatest characteristics of age that we can , even if the plant already has great appearance of age we must enhance this as much as we can. Of course , different tree species will typically exhibit great age in differing ways. An ancient taxus will almost certainly be hollow trunked as may an old deciduous species such as Ulmus , maybe a hedgerow tree stuck many years ago by lightning and slowly rotting from the inside out ever since. An old Picea will feature many jins [ dead branches ] and old junipers will certainly exhibit extensive shari [ deadwood on the trunk ] and jins. The decision about the kind of deadwood that will be appropriate in any given design is where the study and observation of trees out in the landscape comes in. The more interested in bonsai you become, almost inevitably, the more you will begin to use the images of mature trees that you see around you for your inspiration in bonsai design.
A very simple characterisation of deadwood types would see it split into two distinct types. The sort where the removal of bark and wood takes place from the outside of the trunk or branches inwards , that is where we might imagine the tree to have been worn away by the action of wind ,snow, frost and perhaps sand , this type would be most appropriate when creating bonsai with coniferous species. The other kind would be where the wood is removed from the inside of the trunk or branches working toward the outer layers of timber , effectively hollowing out the tree , this emulates a tree rotting outward from the core and would be most often used on deciduous trees. Now like most bonsai 'rules' it will not be right to adhere too closely to this , I have already pointed out that an old coniferous yew would have a hollow trunk and many old deciduous trees feature jins. What is important is that whatever form you use , or combinations of forms ,that it fits with the story that your bonsai is trying to tell about it's past.
Your decision to use deadwood in the design of a bonsai should not involve the gratuitous use of power tools and bits or the ripping of timber technique , but should be the result of the carefully thought solution to a problem in the work , whether that be dealing with a large cut stub of a branch or adding interest to an otherwise plain trunk or simply adding the illusion of age.
And a word of caution here , the presence of old natural deadwood on a bonsai is one of the most prized features that a tree can posess , you need to be very sure about what you are doing before you interfere with it at all , even if it is just to clean it up , it is often very fragile and all to easily destroyed by a heavy hand !!
Finally , it is fine if you do not like deadwood and choose to create bonsai without it's use ,but by the same token you should allow others to create their own images in their own way, live and let live maybe ?