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Saturday, September 4, 2010

How to Make a Dough Bowl Blank

When a piece of wood lands in your lap it's easy to assume you just tear into it and hey presto we have a bowl. This is exactly how I approached the process in the early days but experience has thought me to be just a little deliberate and careful in my assumptions of what the end product from a piece of wood will be. On your left you see a large piece of cedar about 24 inches long and 9 inches wide that I purchased at Reggie's (link for context) along with a few pieces of cherry and some catalpa last week. "What's catalpa?" I hear you ask. Well that's another blog post my friends.

In the picture above you may assume that this blank is fit to produce the mother of all trenchers at 24 by 9 however a closer inspection shows some problems not immediately apparent. On the right you see a picture of one of the largest cracks in the wood. Wood splits like this because variations in the moisture content across the wood cause pressure differences within the grain. This will happen in any piece of wood that is not dried in optimal conditions.  You can see at A the crack dives through the end grain and follows a track along the grain B into the block of wood. This crack will generally become shallower until it eventually disappears.

Another large problem with this process is determining just how the knots have behaved in the drying process. In the picture on the left you can see two knots and three cracks B that could have serious ramifications for the outcome of the carving process. A knot like this can compromise the integrity and validity of a bowl as an instrument of utility and render it a pretty but useless lump of wood in the general shape of a dough bowl. You can also see another but much shorter end grain split at A. In the end these pieces of the block are useless to me and need to be removed to determine just how much of this blank is valid for carving.

It's tempting to try to maximise the size of the bowl
blank at the expense of integrity in order to produce the largest possible bowl. I'm a firm believer that the quality of the bowl trumps the quantity of the bowl every time. I want to produce a flawless bowl so that I know if the customer is dissatisfied with the product it's just a genuine difference of opinion rather than a compromise on my part. That said the knots that produce so many cracks and problems also create beautiful grain. I feel it's best to cut the blank as close to the knot as reasonable and carve back to a clean line in order to capture those beautiful grains in the bowl.

When you have determined the cut lines it's time to saw. At this point many woodworkers will power up the band saw or table saw and Bob's your uncle. I however have not yet invested in one of these fine instruments of efficiency. Growing up in Ireland I took five years of shop in  high school. The Irish shop teachers didn't believe in power tools. This article of faith was reinforced by pathetic Department of Education funding. They truly felt that if you didn't know how a hand saw or chisel felt in the wood and how it would react you just didn't know wood. There are many wonderful wood workers that produce works of wonder on power tools to contradict this theory. However, my experience has been that after a twenty odd year hiatus from wood I was able to pick up a very cheap saw and cut a perfect right angle across a 4 inch thick piece of walnut with no hesitation. It literally saved me thousands of dollars in power tools I'd have to purchase otherwise.

 Here you see two options when it comes to which direction the shape of the bowl should follow in relation to the grain of the wood. The first example shows the bowl cutting thought grain, diving towards the pith or heart of the tree. The other example shows the opposite. You'll notice that the second example will travel with the grain rather than crossing it meaning that the bowl will have very little grain detail in the finished product. Also the fact that that bowl travels away from the pith means that the bowl will have very little detail in it's crater with an awkward looking concentration of grain at the rim of the bowl. This in my opinion produces an imbalanced bowl that never looks comfortable in it's own skin. Try this test. Search wooden bowl in google and go to images. Compare the images of the bowls with the pith or concentration of grain at the bottom of the bowl with those that have the pith in the center or top of the bowl. Which to you looks more attractive and well hued. There are times that you have to travel from the pith when carving or turning a bowl. Knots, checks, cracks, and bark edges have sometimes  much more to say about the outcome of the grain pattern of a bowl than I do. 

It's now time to map out exactly how your bowl is going to look. There are many different formulas that I use to determine this and sometimes none at all. One I particularly like and have been unconsciously using for some time is the Golden Ratio . This was apparently discovered by the Greeks and then Blah Blah Blah, check out the wiki thing. Suffice to say it produces a pretty and proportional bowl. First draw a square by placing the point of your square at the corner of you blank  mark the edge of your square (B) and then have this square again using the same square technique. This produces the point A which is used as the fulcrum for you compass to scribe the line C.  Now if your really cool you'll make the curved ends of the bowl a perfect Fibonacci spiral ark but really you'd only be getting as crazy as me.

  So now you have the plans laid and the tools primed. It's time to carve. On the left you can see the finished product and hopefully see the fruit of our planning and execution. The bowl is proportional, not to long against it's width. The curve is comfortable with the other proportions. The grain is detailed and works with the shape of the crater of the bowl, adding great detail to the overall aspect of the entire work. "Wait a minute!" I hear you exclaim, "how did that lump of wood become this finished bowl?" Well that my friends is a whole other blog post. Happy carving....or what ever it is you do.