What is Raku?

Raku is a firing process that can produce a number of special effects such as metallic sheens (especially copper), crackled glazes and blackened (smoked) clay. The clay item is first bisque fired in a normal kiln and raku suitable glazes and slips are then applied. The raku kiln is designed to raise the temperature of the items very rapidly (in maybe only 15 or 20 minutes). Tongs are used to transfer the hot piece to a container (e.g. a metal dustbin) containing combustible carbon-based materials such as wood shavings, sawdust, shredded newspaper, or even dried leaves. More may be thrown on top. Once the material bursts into flames, an airtight lid is placed on top to create a carbon-rich reducing atmosphere around the pot. The raku process is only really suitable for decorative pieces since the clay body remains slightly porous making it unsuitable for functional items involving liquids or food.

Did Paul Soldner invent raku?
Not exactly. Soldner is an innovator and one of a few responsible for popularizing raku in this country beginning in the 1950's. Raku was first developed by Korean potters under Japanese rule in the 17th century. The circumstances that led to its launch and spread are somewhat of a mystery though.

Artwork i like his pieces they are calm and very nice to look at.

Cone 5-6 glaze recipes

GLAZE RECIPES Cone 5-6 ElectricBarbara Hanselman, ClaysmithThe following recipes have kindly been put together by Barbara Hanselman, Cherry Hill, NJ, USA.
XAVIER’S WARM JADE GREEN - A food safe semi-matte, butter finish glaze.
Talc.......... 9.0%
Whiting.......... 16.0%
Custer Feldspar....... 40.0%
3124 Ferro Frit...... 9.0%
EPK..........10.0%
Silica 325.........16.0%
ADD:
Copper Carbonate......4.0%
Rutile..........6.0%
Brushing Medium..... 1.8% [add only if brushing on]
You can vary the Copper Carbonate from 3-5% with great results and still be food safe.
SAPPHIRE BLUE - a Ron Roy reformulated recipe which breaks nicely on edges.Breaks green on light clay bodies, black on dark clay bodies.Apply medium to heavy.Good for functional and decorative ware.
Frit 3134.......... .37.0%
EPK.............26.0%
Silica 325..........17.0%
Strontium Carbonate..... 4.0%
Custer Feldspar ........16.0%
ADD:
Cobalt Carbonate...... 2.5%
Rutile............ 4.5%
Bentonite.......... 2.0%
Brushing Medium......1.8% [add only if brushing on]
CURRIE BLUE - A butter finish matte which has a lot of interest, breaks nicely and holds it’s own on all clay bodies.Very opaque but with interest.
Ferro Frit 3134............ 10.0%
Nepheline Syenite.........65.0%
Strontium Carbonate........23.0%
Lithium Carbonate......... 2.0%
ADD:
Copper Carbonate..........4.0%
Cobalt Carbonate......... 0.15%
Bentonite.............2.0%
Brushing Medium.........1.8% [add only if brushing on]
BACH’S BLUE GREEN- A glossy semi-transparent glaze which holds on even the darkest clay bodies.Overlays well with Randy’s Red; great over blue, green & red oxide stains.

G200 Feldspar..........27.00%
Silica 325 [flint].......... 20.25%
Whiting.............. 20.25%
Ball Clay [OM4]......... 10.25%
Gerstley Borate.......... 9.00%
Zinc Oxide............. 6.75%
Soda Ash............. 6.50%
ADD:
Zircopax.............. 6.00%
Copper Carbonate......... 6.00%
Bentonite............... 2.00%
Brushing Medium.......... 1.80% [add only if brushing on]
WEATHERED BLUE - a true weathered looking glaze from Pete Pinnell.
Nepheline Syenite.........40.0%
Dolomite.............18.0%
Silica 325............... 18.0%
EPK.....................12.0%
Bone Ash...............6.0%
Lithium Carbonate..........4.0%
ADD:
Zinc Oxide.............4.0%
Copper Carbonate..........2.0%
Cobalt Carbonate......... 0.25%
Bentonite.............2.0%
Brushing Medium......... 1.2% [add only if brushing]
LYNN’S GLOSSY GREY & LIGHT BLUE GREEN - A glossy glaze with a lot of movement.Looks best on textured surfaces or over engobes with red iron and red iron oxide stains.
Gerstley Borate....... 50.0%
Silica 325.......... 30.0%
EPK............. 15.0%
Titanium Dioxide........5.0%
For GLOSSY GREY ADD:
Soda Ash...........2.5%
Copper Carbonate.........2.0%
Red Iron Oxide........1.0%
Cobalt Carbonate.......0.75%
For BLUE GREEN ADD:
Copper Carbonate......2.0%
STRONTIUM WEATHERED BRONZE AND WASHED DENIM BLUE - a great weathered-looking glaze.The bronze goes from a clear, bright green to a brownish bruised green and is suited to all clay body colors, although it is best on tans.The denim blue is not tested.
Lithium Carbonate...... 1.0%
Strontium Carbonate......20.0%
Nepheline Syenite.......60.0%
KYOM 4...........10.0%
Silica 325.......... 9.0%
FOR WEATHERED BRONZE ADD:
Titanium Dioxide.......5.0%
Copper Carbonate......5.0%
Bentonite...........2.0%
Brushing Medium.......1.8%
FOR WASHED DENIM BLUE ADD:
Cobalt carbonate.......0.15%
Copper Carbonate......4.0%
Bentonite..........2.0%
Brushing Medium......1.8%
STRONTIUM TURQUOISE MATTE Cone 5 - The ingredients in this glaze are the same as the ones in Strontium Weathered Bronze; only the amounts vary slightly.A beautiful matte turquoise glaze!
Nepheline Syenite.........60%
Strontium Carbonate........25%
Lithium Carbonate.........2%
EPK....................4%
Silica 325..............9%
ADD:
Copper Carbonate..........4.0%
Bentonite............2.0%
Brushing Medium........1.8%
TECO GREEN - A Tom Zwierlein matte glaze based on a Val Cushing recipe.Reminiscent of the green to grey glaze found on American Art Pottery known as Tecoesque.Really greys out to an ugly color on white stoneware if applied too thick but holds it’s own on other clay bodies [from tans to reds to browns] producing different, interesting effects.
F4 Kona Feldspar......51.0%
Whiting..........19.0%
EPK.............15.0%
Zinc Oxide.........9.0%
Silica 325...........6.0%
ADD:
Tin Oxide..........6.0%
Black Copper Oxide.....4.0%
Red Iron Oxide.........0.5%
Bentonite............2.0%
Brushing Medium.......1.8%
METALLIC GREEN - This metallic luster glaze looks awesome on clays with iron - Laguna’s Electric Brown, Hawaiian and Standard’s 266 Brown or over engobes or stains made from red iron oxide.Both the Sky Blue and Ocean variations also produce metallic lusters and look best on iron rich clays, stains and engobes. Three brushed-on coats really cover well; if more translucency is desired, one heavy or two lighter coats do the trick.

BASIC RECIPE
Frit 3269...........27.0%
Laguna Borate.......15.0%
Spodumene..........40.0%
EPK............18.0%
ADD:
Bentonite...........2.0%
Brushing Medium.......1.8% [add if brushing]
METALLIC GREEN -
ADD Colorants:
Tin Oxide......... 6.8%
Copper Carbonate......4.8%
Using the basic recipe for Metallic Green above but changing colorants will give you these recipes
METALLIC SKY BLUE -
ADD Colorants:
Tin Oxide..........6.8%
Copper Carbonate........3.0%
Cobalt Carbonate.......1.5%
METALLIC OCEAN -
ADD Colorants:
Tin Oxide............7.0%
Copper Carbonate.........4.0%
Cobalt Carbonate......... 1.0%
RANDY’S RED & BLUE - a glossy, translucent glaze which works better as a liner or “inside” glaze.The red goes very orange if re-introduced to a bisque firing after a cone 5-6 firing.The blue is very lavender with specs from the cobalt oxide.Apply medium to heavy, especially outside.Can be runny.
Gerstley Borate.....31.0%
Kona F4............20.0%
Talc.............14.0%
Silica 325..........30.0%
EPK.............5.0%
For RED ADD:
Red Iron Oxide........15.0%
Bentonite........... 2.0%
Brushing Medium.......1.2% [add only if brushing]
For BLUE ADD:
Cobalt Oxide........1.2%
BLACK GOLD MATTE - A great bronze black metallic for all clay bodies at cone 5-6; apply medium.
Redart........... 49.0%
Manganese Dioxide.....36.5%
OM4 Ball Clay.......4.0%
Silica 325 [flint]........4.0%
Black Copper Oxide.....4.0%
Cobalt Oxide........2.5%
Bentonite...........2.0%
Brushing Medium......1.8%
This is my favorite of the golden bronze looking glazes!
BRONZE - Bill Shillalie’s version for cone 02-6.This recipe is so similar to my favorite above that I decided to hold on to it and test it one of these days.The other two are more options.
Red Art............46.0%
Manganese Dioxide......35.0%
OM4 Ball Clay....... 4.0%
Silica 325.......... 4.0%
Black Copper Oxide..... 4.0%
Cobalt Oxide........2.0%
Red Iron Oxide....... 2.0%
Dark Rutile.........3.0%
BRONZE 2
Red Art ............48.0%
KYOM4 Ball Clay...... 4.0%
Silica 325........... 4.0%
Manganese Dioxide.......36.0%
Gerstley or Laguna Borate ... 8.0%
[Used by Virginia Scotchie]
BRONZE 3
Red Art............60.0%
KYOM4 Ball Clay...... 5.0%
Silica 325...........5.0%
Manganese Dioxide........45.0%
Gerstley or Laguna Borate....30.0%
Cobalt Carbonate........ 5.0%
Copper Carbonate....... 5.0%