: Pres - Viewing Profile

I am using Laguna B-3 Brown clay with a 10% shrinkage to build Native American flutes. I extrude 1.1" and .825" diameter tubes as the starting point for the flute bodies. These should shrink to 1" and 3/4" after firing. The length of the tube determine the fundimental tone and the diameter and placement of 6 holes sets the scale notes.

So here is the crux of my post..
1. How much shrinkage occurs from wet to leatherhard stage? From leather to bone dry?
2. I have been tuning the flute during at the leatherhard stage. Should I tune sharp (sharp equals larger hole) by 10%- leatherhard shrinkage as an estimate of pitch?
3. How hard will it be enlarge the holes after cone 6 firing?o

Has anyone had experience flute making that could give their two cents worth? I know, "test, test, test."

oldlady, on 18 May 2013 - 11:39 AM, said:

The Clay King Slabmaster is made by Friendly Corporation, same as Shimpo rollers and Axners rolling Thunder. The studio I belong to has the Shimpo version which looks a lot like the Slabmaster and I have used it and like it. I'll take into consideration a longer working surface. He suggested the cover so I wouldn't have to worry about hitting the rollers and maybe that I could use the cover as a shelf to hold whatever tools I needed while using the table. The shelves are a must and kind of planned to measure whatever space I had on the table Slabroller I get and install what ever configuration would work. I LIKE your idea of clay on a rolling platform makes much more sense than hefty those blocks around.

My main work surface is a worktable I got a SAMs it's tall enough I can stand to work or use the tall rolling stool I have. I think its 5 feet long and super heavy duty with steel legs and a butcher block top and can take a beating so seems to be working out. Unfortunately the top is sealed under varnish so clay seems to like to stick to it and I have thought about getting out the sander and attacking it but for now a piece of canvas seems to be working. I want to get a piece of that board from a Home Depot next time I head that way but haven't made the hour plus trip out that way recently. I even added a shelf under it, with the bonus of its at a good height for me to put a foot if I want. I keep all my plywood and drywall ware boards standing on the shelf and for now clay, my rolling pin and slats on the other side. If I make the rolling platform like you have for my clay I might add a couple more shelves on one side and keep additional supplies there. I even made a small shelf for the end out of 1x4s with each shelf being tall enough to hold pints of underglaze and glaze it ain't pretty but the shelves are level and I used zip ties to attach it to the table legs so it doesn't fall over. Kind of maximizing my one work surface. I would REALLY like to find another table to have dedicated for glazing but not sure where I would put it, might have to get rid of my easel lol. You have no idea how shocking that idea is to me as a painter; my friends would be convinced i was an alien if they even heard that I would consider sticking my easel in the closet.

I also need to figure out someplace to put some shelves to dry ware on, currently I am using a repurposed drying cabinet from my darkroom days to store pieces under construction as well as slowly dry finished pieces. I bought some of that plastic grid made for light covers and use that as the shelf so the pieces don't fall through the widely spaced wire shelves that came with the cabinet. But I can see quickly outgrowing the cabinet as I get stuff made. Just have to decide if I should get one of those rolling wire shelf units from SAMs so I could move it around as needed or just cut up some of the scrap plywood in the garage and screw them to the walls. Will have to think that through some more.

So yes I know and understand multi purpose work spaces and the suggestions you made will be remembered and taken into account as I try and get set up so I can work without moving stuff around every time I want to work on a different piece.

A tip or two for ya' on kiln building and design............

One of the common causes of cold floors on kilns revolves around the mistaken understanding that so many people have that "heat rises". That preception being some sort of a "law" comes from our experiential understanding of our lives....where we experience that HOT GASES rise (like in heated structures). Hot gases rise when suspended in colder gases. Heat energy....... not true.

This mis-understanding is a core concept that I deal with in my Kiln Design and Construction classes.

Heat energy ALWAYS moves from areas of higher concentration to areas of lower concentration. Basic law of thermodynamics. Entropy. Water flows downhill. (Yes... a heat pump can move heat energy seemingly "uphill",...... but that is a separate subject.)

If you want the kiln to fire as evenly as possible using as little fuel to accomplish that feat as possibe........ make sure you don't under-insulate the floor. Otherwise you'll have to adjust the heat DISTRIBUTION pattern in the unit to send more of the overall energy into the floor area than otehrwise necessary.... some of which to also be lost out of the underinsulated floor..... and costing you money in every firing.

So if you decide that the walls and roof structure of a kiln has to have a specific insulation value (heat loss in BTS/ Sq. Ft. / hr.) then the FLOOR should have the same level of insulation. (See * note below also) So if your walls are 9" of brickwork compoised of a 4 1/2" hard brick hot face layer, backed with a 4 1/2" insulating brick layer (of some specific use temp rating) then the floor should also have about this same rating overall.

This can be a little different due to the typical layout of floor bricks being set in the 2 1/2" high layer and the walls being in the 4 1/2" format..... but you CAN lay floors with the brick set in the same (or similar) configuration. The common choices to "match" up to a 9" wall section oftten comes to a decision between a 7 1/2" thick floor and a 10" thick floor. If you understand the insulating values of refractories, you can achieve the SAME insulating value (BTU / Sq. Ft / Hr. conductivity) out of a thinner floor wall section than the side wall structure using DIFFERENT materials........ so the thickness is actuall irrelevant.

The important concept is that the INSULATING value be similar.

The old Rhodes book showing so many 5" thick hardbrick floors in kilns is responsible for SO many kilns with cold bottoms it is amazing. This is something that I commonly end up fixing on a kiln when I am called in to troubleshoot some kiln firing issues.

And if you decide to use fiber in the floor area........ make sure not to compress the fiber too greatly (difficult in a load bearing situation). The more you compress the dead air spaces... the more the loss of insulating value. There is an optimum level of compression for fiber...... used in stuff like Z blocks. Best (easiest) to use "hard versions" of fiber for floors....like board forms.

best,

......................john

(*NOTE: Because there is typically less free air circulation across the cold face of the floor structure, technically the amount of heat energy disappated into the surrounding environment off the cold face is lower than on the vertical wall surfaces and off the roof or arch. So the BTU /Sq,. Ft. / Hr. loss values there is slightly less than the same construction in a wall or roof. But this factor is so small in the overall picture ...as to be inconsequential.)

Today I had five people ask for 'honey pots'.

Ignoring the obvious smart-arse potential, I figured out that they meant 'medium sized jars with an aperture in the lid'.

I had none. Nor do I plan to make any. Oh well...

Marcia Selsor, on 19 May 2013 - 10:07 AM, said:

Thanks, I'm just having fun. The only stress I have is my rooster with 3 inch spurs keeps hiding in bushes so he can jump out and stick a spur 2 inches into my leg while I'm carrying a wareboard full of mugs to the kiln. But I am a bit concerned about you. The last time I was in school semesters were quarters.

Jim