flattopkiln complete

8/12/2019 FlattopKiln Complete

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One of the most difficult andimportant factors to consider

when planning to build a kiln is thekiln’s "scale." The potential size of akiln is thoroughly discussed, debatedand pondered whenever a potterdecides to build a kiln. Kurt Wild and

I have tried to address some of thequestions about scale that arise whendesigning and building kilns.

Without question, the mostimportant question to ask whenconsidering the scale of a kiln is howmany pots can you make in a specific

amount of time? Just how heavy isyour production? Be honest withyourself. Make sure that the kiln thatyou build fits your productionschedule and accommodates the sizeof the pots that you make.

Building a large kiln, andthen agonizing over how to fill it withenough work in order to fire it on a

reasonable schedule, is a waste of yourtime and energy. Many potters areexposed to large kilns in school or thegas kiln at the local art center. Theseare high-production kilns, used bymany people, making hundreds of

h

Keeping in mind that the flusize does not need to change and theburner system is constant in a large orsmall kiln, you can build a kiln to suit

your situation. These kilns can bebuilt to use natural or propane gas. Asmall gas kiln can use a limitedamount of fuel and be as safe aselectric firing—just a simple shed roof is all that is needed for cover in mostsituations. I have built several of thesekilns in garages. Just keep in mind thata good amount of space is needed

around any fuel kiln.

As always, you need toobserve some caution when building akiln! Please check with your localbuilding/zoning department and thefire department for area regulationsbefore moving ahead with this project.It would also be prudent to contact

your insurance carrier about yourcoverage. It is better to be prepared

before you start, rather than makingchanges after you are finished.

These plans are meant to be abasic guide to building the kiln. Youcan take these plans and modify themto fit the space and size of the areah l i I i

obtain a copy of "The Art of Firing"by Nils Lou. This book contains awealth of information on building andfiring kilns, especially the Minnesota

Flat-Top.

The Building Process

The FoundationThe site for building the kiln

should be a flat, clear area with acompacted gravel base or a concrete

slab. The base for the kiln and stack

are constructed using a combinationof 8-inch and 12-inch concrete block.This kiln has a layer of 8-inch blockpositioned so the holes in the blockrun horizontally to allow air to passunder the kiln. A layer of 12inchblock with the holes in a vertical

position is placed on the smallerblock, overlapping the seams. Another

layer of 8-inch block is placed on topof the 12-inch block in the samepattern as the bottom layer. (SeeDrawing 1)

Once the concrete block is inplace and level, place the expanded

l b d h

Building a Small Flat-top KilnBy Mel Jacobson and Kurt Wild

Make your dreams of having a fuel-fired kiln come true with these flexible plans



middle layer of softbrick should bechanged so the joints are staggeredbetween layers. You should pay closeattention to maintaining a level, flatsurface with each layer of brick. Thisattention to detail will help ease theconstruction of the rest of the kiln.

(See Drawing 2)

The Walls

The first course of the wallis a soldier course. The bricks areplaced on edge so the layer is 41/2

inches high. You should start withthe back wall (See Drawing 3) toposition the flue (41/2 x 7 inches) and

the burner ports (41/2 x 41/2 inches).You will notice that the flue openingis just slightly off center on thedrawing to allow for use of a fullbrick on one side. This will not affectthe kiln’s operation. Continue withthe soldier course and allow for thedoor opening. These plans show the

door on the front wall of the kiln(See Drawing 4) but in Kurt’s kiln the

door was placed in the sidewall.Either option will work. Someinsulation bricks will need to betrimmed to size using a hacksaw or aregular handsaw.

Once the soldier course iscompleted, continue building the

walls. Rows 5 through 16 are laid inalternating courses (See Drawings 5

and 6). When starting to place thebrick for row 5, you may need toadjust the brick on the back wall sothat there aren’t any joints above thefl b t i B

The Roof

The roof consists of insulating firebrick stacked on end inmultiple rows and clamped together.The first step is to cut out a 3/4-inchplywood deck that is just slightlysmaller than the inside dimensions of

the kiln chamber. Be sure to includethe opening left in the wall for the

door. This piece is mounted in thekiln using 2x4 braces placed at aslight diagonal to allow for easyremoval when you are finishedbuilding the roof. Be sure to useplenty of braces around the perimeterand in the middle of the form. The

top of the plywood should be slightlyhigher than the kiln walls to allowfor the thickness of the ceramic fiberplaced on top of the wall as a gasket.

Tip: Place a chalk line ontop of the plywood to mark thecenter of the kiln from front to back.This line will help keep the roof

square while placing the brick on topof the plywood.

When placing the brick inposition, dip the top 2/3 of eachbrick in a very thin slip made up of equal parts fireclay, common sandand water. This slip should be thickenough to lightly cover the brick’ssurface, not just stain it. Not coating

the whole brick will prevent clayparticles from falling into the kiln

during the firing. The clay slip on theother part of the brick will help holdit in position when clamped togetherin the next step.

S t h b i k i iti

Tip: Although you canperform most of the constructionprocess as an individual, it is a wisedecision to enlist help from others forseveral of these steps, especially whenbuilding the roof.

You are now ready to place

the corner braces and tie rods inplace. Make the four corner braces

by welding pieces of 21/2 x 21/2 x1/4-inch steel angle together and drillingholes in the appropriate locations.(See inset on drawing 7) Position thebraces, add the tie rods, nuts andwashers, and snug them up evenly.Place hard firebrick splits between

the brick and the tie rods on eachside of the roof (See drawing 7)before tightening the nuts on the tierods. This will keep the bricks frombowing out or the tie rods frombowing in during the tighteningprocess.

Once you have applied a

slight tension to the roof structure,remove the middle inside support.

Replace this support with a shorterone and a hydraulic jack. Raise thecenter of the roof about 3/4 inch tocause a slight domed effect. Continuetightening the tie rods in an equalmanner working from front to backand side to side in several steps. A

torque wrench is recommended andyou should tighten to about 40 ft/lbs

of torque. The roof is now a slightlydomed, solid slab. Once you fire thekiln, you will want to re-tighten thenuts to 40 ft/lbs to allow for anyt t hi f th t l ti d



inch thick angle iron that isapproximately 76 inches in length oneach corner joined by tie rod orcable. A unique feature on Kurt’s kilnis the use of 1/8 inch steel cable andeyebolts to join the corners together.The eyebolts are placed in holes

drilled through the angle iron. Theholes are drilled so that the top holes

are 2 inches above the roof and thebottom holes are 4 inches below thehard brick floor. One end of thecable is looped through the eyeboltand fastened with a cable clamp. Theother end is passed through theopposite eyebolt, pulled tight and

fastened with a cable clamp. Whenall 8 cables are in position, slowlyand alternately tighten the nuts onthe eyebolts to create an even tensionon all the cables.

The Flue Box and Chimney StackThe flue box is designed to

create a double Venturi effect on thegases coming from the kiln chamber.

This system of restricting, thenexpanding, then restricting andexpanding again is used to create astrong draft of the flue gases andturbulence within the kiln chamber.

The flue box uses acombination of hard brick laid flat

and soldiered to make the 1-inch slotfor the damper (see drawing 8). The

damper is made from a 1-inch thickpiece of Kaowool "M" board. Thetop of the flue box is the second areaof restriction before entering thehi t k Thi i i th

sit on a piece of the ceramic fiberboard or blanket to provide anairtight seal against the brick of theflue box.

The chimney on Kurt’s kilnis 10 feet in height. The height canvary to some degree without affecting

the firing of the kiln. If your kiln isgoing to be located inside, the

chimney needs to extend through andbeyond the peak of the roof. It willbe supported and secured by the roof structure. If the kiln is outside, youwill need to support the stack eitherby having a shed over the kiln orusing a guy wire system to hold the

chimney in place.

Burners

The burners for this kiln caneither be a high velocity propane ornatural gas with forced air. Yourburners should have the requiredsafety devices such as a

pilot/thermocouple safety shut off system and be installed to meet safety

codes in your area. The burners areplaced on either side of the chimneywith the flame entering the chamberagainst the inside of the wall. Targetbricks can be used to direct the flamewhere needed. These bricks can bemoved to fine tune the firing of the

kiln.

Other Notes

The internal measurementsof Kurt’s kiln are 311/2 inches wide by36 inches deep by 341/2 inches highf t t l f 22 6 bi f t

shelves are placed so there is a 6-inchspace on both the back and front sideof the shelves to act as the flamewaysfor the burners.

Materials list for Kurt Wild’s versionof the Minnesota Flat-Top Kiln:

51 Standard 8-inch cement blocks

(71/2 x 71/2 x 151/2 inches)12 12-inch cement blocks(71/2 x 111/2 x 151/2 inches)3 4-inch cement blocks(71/2 x 31/2 x 151/2 inches)

Expanded metal or cement board as

the first layer over the cement blockand before laying the brick. For thekiln proper, 1 48x54 inch piece or 224x54 inch pieces are required. Thestack base requires 1 18x18-inchpiece.

800 K23 insulating firebrick

9x4 1/2x2 1/2 inches (this amountincludes about 20 extra bricks to

cover breakage and or cutting).

220 hard firebrick (straights)(9 x 41/2 x 21/2 inches)8 #2 split hard firebrick(9 x 41/2 x 2 inches)2 #1 split hard firebrick

(91/2 x41/2 x 11/2 inches)2 1 1/4-inch split hard firebrick

(9 x 6 x 11/4 inches)4 thin split hard firebrick(9 x 41/2 x 1 inches)1 21/2 x 41/2x12-inch or 121/2-inchh d fi b i k (f d l t)



10 12-inch Kaowool sleeves(81/2 inch ID x12 inch length;91/2 inch OD), to line galvanizedmetal stack2 5-foot-long sections of heavygalvanized pipe for stack (to be linedwith the Kaowool sleeves). Using

standard 2-foot lengths of galvanizedpipe is not recommended, as the

Kaowool sleeves do not readily slidedown the pipe. Any heating andsheet metal shop can fabricate 5-footlengths. Be sure to provide the shopwith a Kaowool liner to ensure adecent fit.

1 72-inch piece of 2x2x1/4-inchangle iron is required for fabricationof the 4 roof corner braces.

1/2-inch cold rolled rod is required toconnect the roof corner braces:4 52-inch long pieces are required forthe sides

4 45-inch-long pieces are required forthe front and back (each rod must be

threaded 3 inches on each end).16 1/2-inch nuts are required and 161/2-inch washers.

4 Corner, upright angle iron braces(2x2x1/4 inch) 76 inches in length.1/8-inch steel cable to fasten upright

braces (you may want to have thecable cut to size at the hardware

store as it is difficult to cut withoutproper tools). This kiln required 4pieces, 56 inches long and 4 pieces,48 inches long16 5/16 4 i h b lt



Stack



(See Materials Listfor rod length)

Corner Bracket

flattopkiln complete

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