Should all bowls have uniform wall thickness?

[Steve Mathews]

I'm about to make my first attempt at a bowl that doesn't have a simple shape and was wondering if the inside wall should conform to the outside and have a uniform thickness? Or should the inside be more traditional? The first bowl planned has a slight ogee shape on the outside. The other is shaped like a donut but has a small opening.

[Don Orr]

Tough question to answer without a better idea of actual desired outer shape. Also I think it depends on its intended use. Are they meant to be functional like a salad bowl or strictly decorative. An ogee shape can be both with fairly even walls-maybe slightly thicker in the bottom for stability. The donut/small opening sounds more like a decorative hollow vessel where, if you can't see the inside the thickness does not need to be exactly the same all the way but should be mostly even with, again, a little weight in the bottom. This is of course just my opinion and worth every cent you paid for it.

[Reed Gray]

The only way to have perfect even wall thickness is if you make one of the earthquake indicator bowls, which is half a sphere and has a round bottom. There is always some extra thickness through the transition areas of the bowl. The biggest difference it might make is if you twice turn your bowls, rough turn and leave it thick, dry, then turn to final thickness. If you are way off on the rough turn, it can put uneven stresses on the bowl during the drying and cause cracks. Some people like a slightly thicker and under cut rim for a better thumb grip, though it feels strange to me. Eventually you will get a 'feel' for what is right. After years of selling, it still astounds me how much people want to pick up and feel the bowls. Part of why I don't try to sell on line because you can't just pick them up and hold them. I prefer clean simple lines. Some like all sorts of curves, just depends...

robo hippy

[JohnC Lucas]

If it's green wood it helps to have the wall thickness the same. If it's dry wood anything is fair game. I have bowl I kept downstairs that is about 4" thick. I like it. I also have one that I kept that is just a hair over 1mm thick. On dry bowls you can also make the walls of the bowl vary in thickness. With green wood you risk it drying unevenly and cracking if the wood isn't the same thickness.

[Prashun Patel]

It is good technical technique to keep the wall thickness uniform and many times this is also an aesthetically pleasing thing to do.

However, if your bowl is properly dry, then making the bottom thicker can sometimes be preferable for feel or balance. Specifically, I often do this on bowls that are as tall as they are wide, and on bowls that have a pronounced curve at the bottom; Something about the way these are cradled and held around the bottom makes me want them to have a thicker bottom. I like big butts and I cannot lie.

[John K Jordan]

I'm about to make my first attempt at a bowl that doesn't have a simple shape and was wondering if the inside wall should conform to the outside and have a uniform thickness? ...

My opinion, no.

To me, a bowl that gradually thickens towards the bottom sometimes has a better feel in the hand, better balance. One with a thicker and heavier base will also be more stable for something that will be used rather than looked at - the bowl of the mortar and pestle I made recently is quite thick overall but considerably thicker at the bottom (and the foot is wider than some wood "artists" like but that also makes it more stable in use.) I do this for stability on Beads-of-Courage boxes too since some sick kids may not have as motor control.

Turning a thick base on very wet wood of some species may give it more of an opportunity to crack, but I found this is no problem if I leave the wall relatively thick and uniform in the roughing stage, dry very slowly, then finish turn the dry wood with the base just how I want it. No cracking this way even with a thicker wall at the base. Since a thicker rough-out will take longer to dry this might not be attractive to the impatient.

Richard Raffan writes about this in his books. He recommends something few have the guts to do - turn some bowls then cut them in half with the bandsaw to see the actual cross section. After a few of these it should be obvious what type of thickness cross section results in a bowl that feels better when handled. I did this with one of my hand bell ornaments to show people the wall thickness (and construction):

bells_cutaway_IMG_5169.jpg

BTW, I seem to get more positive verbal comments on pieces of identical designs when I hand them one thicker and heavier. I think people sometimes associate thinner and lighter with lower relative value.

If you don't like the look of "fat" walls, making the rim thinner makes the whole piece look thinner. I just finished some hand bell ornaments that are close to 1/4" at the top but thin smoothly down to about 0.020" at the rim - the entire bell looks and feels very thin but is much stronger with increased thickness away from the edge. The one in the photo above is not turned as thin as the new ones but it shows the gradual thickening.

JKJ

[Terry Vaughan]

There may be practical reasons to make the bowl thicker at the bottom, or as equal as possible, but I disagree about the feel. It's purely subjective, but to me a bowl feels better if it's a little thinner at the bottom. Thicker seems a bit clunky somehow. But that's just me. Everyone has their own style. Most of mine have a pedestal foot of some kind. Often when I've finished a bowl I wish I'd cut a bit deeper.

[Steve Mathews]

Here is the ogee shaped bowl that I talked about at the top of this thread. I'm not sure why I decided on this shape but recall making a mistake while roughing it out had something to do with it. It hasn't dried enough to finish but I wanted to get some ideas beforehand. I also included pics of another bowl turned about the same time that has a more traditional and simple shape. Both are Mesquite and were a joy to turn. And no cracks yet after a month of drying.

Mesquite Bowls 001.jpgMesquite Bowls 002.jpg
Mesquite Bowls 004.jpgMesquite Bowls 003.jpg

[Steve Mathews]

John,
That hand bell ornament is beautiful! It would've made me sick to cut it in half.

[John K Jordan]

John,
That hand bell ornament is beautiful! It would've made me sick to cut it in half.

Thanks! Those ornaments are one of my favorite things to make. I'll try to get some photos soon.

That one is made from Brazilian Tulipwood (a rosewood) and a Bloodwood handle - it was one of my favorites! BTW, I love turning Tulipwood but unfortunately it is now an endangered species.

I took that one and some other small turnings to Europe to show friends and people we met. I was disappointed at first when I discovered the big chip it somehow got in my backpack. But good can come from misfortune - I decided it was perfect for illustrating how I shape the bell - a real thing to hold in the hand is so much better than a drawing! I've since made a duplicate.

I'm working on a document on making these for my next demo and I think the picture of the one cut in half will be good there.

JKJ

[Dale Bonertz]

I also say no they don't have to have even thickness. The uneven rim bowl you showed in the other thread is an instance that the high and low points should be pretty even. On a cut rim bowl like the ones you show in this thread don't need to be even. If you get the Raffen book his salad bowls on the inside has a subtle undercut then they go down a slight taper to about 2/3 from the rim is the thinnest spot and then it gets slightly thicker at the base. It is still a continuous curve and has a very nice feel inside but he has good points for doing so. The undercut is so when you hold the bowl with one hand the thumb can grip the bowl without it slipping out of your hand. The thinner spot at about 2/3 down from the rim is to help reduce weight of the bowl for easier handling. The slightly thicker base (not clunky thick) is for as mentioned stability. He will also recommend a base of 1/4 to 1/3 the width of the bowl for stability i.e.: 12" bowl should have a 3" to 4" foot/base. If you are wanting to turn bowls I would highly recommend his book "The art of Turned Bowls". Well illustrated and written.

[John K Jordan]

...If you are wanting to turn bowls I would highly recommend his book "The art of Turned Bowls". Well illustrated and written.

That's a great book. Another one I think worth reading is Mike Darlow's "Woodturning Design", https://www.amazon.com/Woodturning-D.../dp/1565231961 Some people don't like Darlow due to his detailed technical approach which requires some effort to get the most of (the opposite of a YouTube video!) but I consider him one of the best at making me think. For example, his discussion of the golden mean is enlightening. (I basically learned turning from Raffan's and Darlow's books.)

JKJ

[Dale Bonertz]

I also have Darlow's book and you a right sir it is another great book. I also believe Ellsworth's book is very good and others that I have read. Reading is learning, they all have good to great information.