325 mesh | 3D Design | 3D Printer | 3D Slicer | 3D-Printed Clay | 3D-Printing | Abrasion Ceramics | Acidic Oxides | Agglomeration | Alkali | Alkaline Earths | Amorphous | Apparent porosity | Ball milling | Bamboo Glaze | Base Glaze | Base-Coat Dipping Glaze | Basic Oxides | Batch Recipe | Bisque | Bit Image | Black Coring | Bleeding colors | Blisters | Bloating | Blunging | Bone China | Borate | Boron Blue | Boron Frit | Borosilicate | Breaking Glaze | Brushing Glaze | Buff stoneware | Calcination | Calculated Thermal Expansion | Candling | Carbon Burnout | Carbon trap glazes | CAS Numbers | Casting-Jiggering | Celadon Glaze | Ceramic | Ceramic Binder | Ceramic Decals | Ceramic Glaze | Ceramic Ink | Ceramic Material | Ceramic Oxide | Ceramic Slip | Ceramic Stain | Ceramic Tile | Ceramics | Characterization | Chemical Analysis | Chromaticity | Clay | Clay body | Clay Body Porosity | Clay for Ovens and Heaters | Clay Stiffness | Co-efficient of Thermal Expansion | Code Numbering | Coil pottery | Colloid | Colorant | Cone | Cone 1 | Cone plaque | Copper Red | Cordierite Ceramics | Crackle glaze | Crawling | Crazing | Cristobalite | Cristobalite Inversion | Crucible | Crystalline glazes | Crystallization | Cuerda Seca | Cutlery Marking | De-Airing Pugmill | Decomposition | Deflocculation | Deoxylidration | Digitalfire Foresight | Digitalfire Insight | Digitalfire Reference Library | Dimpled glaze | Dip Glazing | Dipping Glaze | Dishwasher Safe | Dolomite Matte | Drop-and-Soak Firing | Drying Crack | Drying Performance | Drying Shrinkage | Dunting | Dust Pressing | Earthenware | Efflorescence | Encapsulated Stains | Engobe | Eutectic | Fast Fire Glazes | Fat Glaze | Feldspar Glazes | Firebrick | Fireclay | Fired Strength | Firing Schedule | Firing Shrinkage | Flameware | Flashing | Flocculation | Fluid Melt Glazes | Flux | Food Safe | Foot Ring | Forming Method | Formula Ratios | Formula Weight | Frit | Fritware | Functional | GHS Safety Data Sheets | Glass vs. Crystalline | Glass-Ceramic Glazes | Glaze Bubbles | Glaze Chemistry | Glaze Compression | Glaze Durability | Glaze fit | Glaze Gelling | Glaze Layering | Glaze Mixing | Glaze Recipes | Glaze Shrinkage | Glaze thickness | Globally Harmonized Data Sheets | Glossy Glaze | Green Strength | Grog | Gunmetal glaze | Handles | High Temperature Glaze | Hot Pressing | Incised decoration | Ink Jet Printing | Inside-only Glazing | Insight-Live | Interface | Iron Red Glaze | Jasper Ware | Jiggering | Kaki | Kiln Controller | Kiln Firing | Kiln fumes | Kiln venting system | Kiln Wash | Kovar Metal | Laminations | Leaching | Lead in Ceramic Glazes | Leather hard | Lime Popping | Limit Formula | Limit Recipe | Liner Glaze | LOI | Low Temperature Glaze Recipes | Lustre Colors | Majolica | Marbling | Material Substitution | Matte Glaze | Maturity | Maximum Density | MDT | Mechanism | Medalta Potteries, Medalta Stoneware | Medium Temperature Glaze | Melt Fluidity | Melting Temperature | Metallic Glazes | Micro Organisms | Microwave Safe | Mineralogy | Mocha glazes | Mohs Hardness | Mole% | Monocottura | Mosaic Tile | Mottled | Mullite Crystals | Native Clay | Non Oxide Ceramics | | Once fire glazing | Opacifier | Opacity | Ovenware | Overglaze | Oxidation Firing | Oxide Formula | Oxide Interaction | Oxide System | Particle orientation | Particle Size Distribution | PCE | Permeability | Phase change | Phase Diagram | Phase Separation | Physical Testing | Pinholing | Plainsman Clays | Plaster Bat | Plaster table | Plasticine | Plasticity | Plucking | Porcelain | Porcelaineous Stoneware | Pour Glazing | Precipitation | Primary Clay | Primitive Firing | Production Setup | Propane | Propeller Mixer | Pyroceramics | Pyroceramics | Quartz Inversion | Raku | Reactive Glazes | Reduction Firing | Reduction Speckle | Refiring Ceramics | Refractory | Refractory Ceramic Coatings | Representative Sample | Respirable Crystalline Silica | Restaurant Ware | Rheology | Rutile Glaze | Salt firing | Sanitary ware | Sculpture | Secondary Clay | Shino Glazes | Shivering | Sieve | Silica:Alumina Ratio (SiO2:Al2O3) | Silk screen printing | Sintering | Slaking | Slip Casting | Slip Trailing | Soaking | Soluble colors | Soluble Salts | Specific gravity | Splitting | Spray Glazing | Stain Medium | Stoneware | Stull Chart | Sulfate Scum | Sulfates | Surface Area | Surface Tension | Suspension | Tapper Clay | Tenmoku | Terra cotta | Terra Sigilatta | Test Kiln | Theoretical Material | Thermal Conductivity | Thermal shock | Thermocouple | Thixotropy | Tony Hansen | Toxicity | Tranlucency | Translucency | Transparent Glazes | Triaxial Glaze Blending | Ultimate Particles | Underglaze | Unity Formula | Upwork | Viscosity | Vitreous | Vitrification | Volatiles | Warping | Water in Ceramics | Water Smoking | Water Solubility | Wedging | Whiteware | Wood Ash Glaze | Wood Firing | Zero3 | Zeta Potential

Oil-spot glaze

A mottled glaze created by double-layering glazes of different melt fluidity and color

Details

Officially, the oil-spot variegation effect appears to be the product of the release of gases of decomposition associated with an iron oxide phase change near the climax of a high temperature (cone 8+) firing cycle. The effect appears to be accompanied by the precipitation and crystallization of iron during cooling.

However the oil-spot effect could theoretically be created at any temperature with any color if a decomposition process exists for one of the materials present (or an interaction). The bubbles could be employed to deliver a contrasting color from an underlying glaze layer. Another glaze double-layering method is to employ melts of different fluidity (and contrasting colors). Typically the base glaze is melt-fluid and the over glaze is a lighter non-fluid glaze (typically a matte). The under glaze breaks through and isolates islands of the upper glaze to create the effect. Vertical and horizontal surfaces display the effect differently. The relative thickness of the glazes can be tuned to optimize the aesthetic. More subtle effects can be created by using glazes of the same color but different surface character. With this mechanism it appears logical to tune the chemistry of the overglaze to have a higher surface tension that the lower one.

In our experimentation we have found that tin oxide, in higher percentages (e.g. 6%), bubbles a high-surface-tension base transparent (high SrO content). Thus, over a black, the surface activity created by the bubbling creates a variegated pattern and texture of black and white.

Related Information

Ravenscrag oatmeal layered over black at cone 6

This is GR6-H Ravenscrag oatmeal over G1214M black on porcelain at cone 6 oxidation to create an oil-spot effect. Both were dipped quickly. You can find more detail at ravenscrag.com.

Variegation gone too far!

This is Ravenscrag Slip Oatmeal over a 5% Mason 6666 stained glossy clear at cone 6. You have to be careful not to get the overglaze on too thick, I did a complete dip using dipping tongs, maybe 2 seconds. Have to get it thinner so a quick upside-down plunge glazing only the outside is the the best way I think. You may have to use a calcined:raw mix of Ravenscrag for this double layer effect to work without cracking on drying.

Links

URLs http://ceramicstoday.glazy.org/articles/oilspot.html
Oil Spot Glazes by John Brit

By Tony Hansen


Tell Us How to Improve This Page

Or ask a question and we will alter this page to better answer it.

Email Address

Name

Subject

Message


Upload picture

Please check recaptcha to proceed


Copyright 2008, 2015, 2017 https://digitalfire.com, All Rights Reserved