#Mug #57 - Trimming
#100Mugs100Ways
Day 57
Here is #Mug #57 - Trimming
Trimming a Mug:
In most cases, trimming a mug is required, but there is always an exception to the rule. If the bottom of a mug is left flat, and I desire to leave the bottom simple, there will be no, or minimal trimming required.
I like to discuss why trimming a mug is necessary.
Remove excess clay from the bottom of the mug, which I could not access while throwing.
To achieve a consistent thickness of the walls and bottom throughout.
To create a unique foot that is stable as well as functional.
To give the mug a unique aesthetic look.
To prevent the glaze from running onto the kiln shelf.
Choosing the right timing to trim a mug.
The clay of the mug should be at a leather hard stage. I need to be able to press my fingernail into the clay, and it should be strong enough to be handled without damaging its shape.
Some trimming ideas and hints
I look at the inside shape of the mug and follow that form when trimming the outside.
I want to achieve a continuous shape and look when thinking of the shape of the foot.
Determine where the bottom of the mug meets the sidewalls; this is where the foot should begin. This is not a set rule by any means, but it can be considered and will be aesthetically agreeable.
When an "S" crack occurs at the bottom, there are several reasons for it; one is an uneven thickness at the bottom of the mug. I want to have a consistent thickness in the wall and the bottom of each mug.
How to Trim
Secure the mug to the wheel head or bat with three small clay lugs. Hold the mug with one hand to limit moving it while I place clay lugs. When applying the lugs, it is important to push them down onto the bat without putting pressure on the mug. I used the Hsin-Chuen Lin method to secure the mug to the wheel head, to find out what that method is go to my blog and watch the video.
Before I start, I make sure I know how thick the bottom of the mug is to avoid any over trimming. I use the tapping method and listen for the thickness of the wall or bottom of the mug.
The best way to hold the trimming tool is to have it under my palm of my right hand for strength and stability. Securely I keep my fingers close to the trimming tooltip for good leverage and to avoid chattering. I keep a finger from my left hand on the mug; as I throw, my hands are always touching. I keep the tool position at 3 o'clock on the wheel. The wheel speed should be pretty fast, but not full speed. I then start to remove rough clay from the bottom edge that is in the way.
If necessary, I remove clay from the outside of the foot down the mug's outside wall. Periodically I tap to hear if the thickness has changed, and I remove more clay if necessary.
Now I place the trimming took at the center of the foot and carve away by moving it to the edge of the mug. Then repeat that step, but I stop at about 1/2" away from the edge of the mug. I leave that as the foot. I do this several times and make sure the foot is even and smooth. I frequently tap the mug as I remove clay and listen to the change in sound as more and more clay is removed. This method gives me an idea if I have trimmed enough.
When I have removed all the clay, I examine the mug. I check for any unevenness and make sure the mug looks and feels smooth. To achieve smoothness, I like to burnish at the end of trimming if the clay has grog in it. When examining the mug, I notice pits and scratches caused by the grog, and if not smooth enough, there is a possibility of it having a negative effect on the glaze later. If the clay is too dry, I spray the mug slightly, allowing for burnishing it evenly. I like using a metal rib to smooth and burnish the clay surface.
After finishing, I put my makers mark on the inside of the foot area. To achieve a smooth looking imprint, I use a darning mushroom I made, place it on the inside of the mug for support. Then I remove the mug from the bat and inspect it for any imperfections. I may choose to sand it, if necessary.
The Hsin-Chuen Lin method