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Coil Vessels with Sgraffito

Lesson Submitted by: Justin Kramer
UNIT: Ceramics - Traditional coil - Decorating Techniques - Motif - Symbolism
Lesson: Traditional coil vessels with Sgraffito decoration
Grade Level: Middle School through High School

Objective: To be able to build a clay coil pot that has the following criteria:

Control of media--demonstrates good craftsmanship - traditional symmetrical form

Designed with specific function in mind--container, teapot, etc.

Emphasizes good design--unity, rhythm, form, and balance.

Sgraffito design enhances form - Utilizes personal symbolism

Sgraffito decoration technique: a technique used to decorate ceramics in which the top layer (slip) has patterns scratched into it, revealing the different-colored layer (clay) beneath

Introduction to Creating a Clay Coil Pot Review methods

Present an historical overview of ceramics - show various cultures.

Resources:

Slip information from Marvin Bartel

Books

THE BEGINNER'S BOOK OF POTTERY. PART 1: COIL AND SLAB POTTERY - Coil and slab pottery are covered in this book.

Hand-built Ceramics: Pinching * Coiling * Extruding * Molding * Slip Casting * Slab Work - Triplett offers a guide to basic techniques, from pinch pots to slab-work, with color illustrations of tools and techniques and instructions for eight projects of planters and pitchers.

Materials:

Moist Clay--approximately 5 lbs (2.3 kilograms) - depending on size of pots.
Cloth covered table or board (Canvas Rolls cloth)
Board (8" to 9" (20 - 23 cm) wood or plaster bat for carrying pot)
Plastic bag--large enough for storage of work in progress.
Rolling Pins, Clay Slip and Brushes. Contrasting colored Slip
Scoring and Clay Modeling Tools - Pottery Tool Set - Wire End Clay Tool Set
Small container of water to moisten hands.
Circular base pattern--3" to 5" (7.6 to 12.7 cm) in diameter.
Optional: Cardboard template of pot shape, Masking Tape, Banding Wheels, Kiln
Optional: Tooling Foil - Wire End Clay Tool Set

Directions

Make A Base
Flatten clay with rolling pin - ½" (1.3 cm) thick

Use Pattern as Guide
Cut circle - place base on banding wheel (if available)

Create a Clay Coil
From a small ball - roll out clay until ½" thick with moistened hands.
Keep coil round as light rolling motion is used.

Joining Clay
Rough edge of base and coil with scoring tool.
Apply slip with brush to base.
Gently press coil to base.

Continue to Add Coils
Place next coil on top of first.
Use same joining method.
Optional: Use cardboard template wrapped in masking tape to help control form

Shaping the Walls
The pot's shape may be curved outward or inward depending on placement of coils.
Alternate: Cut ½ (1.3 cm) thick slabs into approximately one inch wide strips (thick slab method). Add an thin slabs as post progresses. This is close to the Korean method of construction.
Optional: Use cardboard template wrapped in masking tape to "waterproof" some what. Use template and metal scraper to control pot shape on banding wheel.

Slip Sgraffito: Apply contrasting colored slip to surface of leather-hard clay and allow to slip dry. Use wire loop tools to engrave design in clay. Carve designs while still leather-hard (to avoid dust) Bisque fire - optional - Clear Glaze. See note from Justin

Embellish with foil tooling accents.

Alternate Forming Methods:

Press mold - pressing clay into bowl shape (using plastic wrap or paper separator) - making two bowls then fusing seam together. Add neck and foot to vessel.

Shape coils around a balloon to help control shape.

Assessment:

Student is able to:

Describe the coil pot building process and apply this understanding to creating an actual coil pot.

Demonstrate good craftsmanship through the final appearance and construction of the pot

Create personal symbols and unified design with Sgraffito decorating technique.

Rubric Revised from Marianne Galyk

Assessment Rubric
Student Name:						Class Period:
Assignment: Traditional Coil Vessel - Sgraffito decoration.						Date Completed:
Circle the number in pencil that best shows how well you feel that you completed that criterion for the assignment.	Excellent	Good	Average	Needs Improvement	Other	Rate Yourself	Teacher’s Rating
Criteria 1 – Sketches showing use of elements and principles of design- motifs/symbolism planned and researched	10	9	7-8	6	0-5
Criteria 2 – Traditional coil vessel - symmetry - functional form - smooth surface.	10	9	7-8	6	0-5
Criteria 3 – Symbolism and motifs enhance form - clearly etched in surface - slip evenly applied.	10	9	7-8	6	0-5
Criteria 4 – Effort: took time to develop idea & complete project? (Didn’t rush.) Good use of class time?	10	9	7-8	6	0-5
Criteria 5 – Craftsmanship – Neat, clean & complete? Skillful use of the art tools & media?	10	9	7-8	6	0-5
Total Possible: 100 points (Average score x 10)						YOUR TOTAL	Grade

Note from Justin:

I use a mid-fire terracotta clay (fires to a earthy red colour). When the students have finished hand-building and the clay is leather hard they apply a coloured slip. The coloured slip is made from white earthenware (usually dried pieces leftover from other projects that is put into a blender with water to make the slip). Added to the white slip is a clay body stain - you can get a range of colours including blues, reds, oranges, yellow, green, etc. This is applied thinly onto the surface. It is easier and healthier to scratch into the surface of the clay while it is still leather hard - i.e. before it is completely dry this avoids making fine dust.

Note from Judy Decker:

I didn't want to gamble with my limited knowledge chemistry and problems with "fit".... I bought Amaco slips. The natural black is a rich brownish black. Jet black is a bluer black. When I wanted a pure black, I bought black underglaze which worked similar to black slip. I used brown, white, blue and black Amaco slips. They come in powdered form and you mix what you need. The Underglazes come in 16 oz. containers in liquid form. I used black, white, blue underglaze the same way as slip (as the blue underglaze was also a darker blue - more towards cobalt that the slip).

How to make Slip from Marvin Bartel:

I often use several colored slips that are put on the pot while clay is soft or no harder than leather-hard (for satisfactory slip adhesion). To encourage students to think artistically, I assign them to to use at least three different size sharpened stick points for line variation when scratching their designs, patterns, motifs, etc on the clay. No pin point tools are allowed on their first efforts because the glazing hides it too much when the lines are too thin. I encourage bold, simple, and fairly quick approaches until they see some finished results.

In my work, my favorite drawing tool is a quarter inch diameter wood dowel rod, not pointed, but left with a square cut end. When I draw with the corner of the square cut end, it gives line thickness variation adding movement and life to the lines. I only work on wet clay to avoid dust. I leave the burrs around the scratches. Before glazing, I rub the burrs off of the bisque with a small piece of broken kiln shelf or a hard piece of broken brick. Bisque dust is not so fine and is much less apt to get airborne and hazardous to breath.

I show no examples, but I have students practice on clay scrap before doing it on the projects. For ideas, they make sketches and make lists about themselves. We study cultures as a follow up after they have fired some work. Our work is to express our selves and our culture just as their work expresses themselves their culture.

Simple slip recipes I use:
Since slip does not melt, you do not need to be accurate for slip as you would for glaze recipes - use any convenient measuring device.

Brown
1 scoop of red iron oxide
3 scoops of the same clay used for the pots (dry scrap is okay)
Put it in water. Let it set quietly until the clay is mushy. Stir until thick as coffee cream.

Blue
1 spoon cobalt carbonate or oxide
9 spoon of Dry Clay (It's getting difficult to find dry clay. Most comes moist now.)
I add some liquid blue tempera to make it look blue when using - just guess at this.
(Cobalt is toxic if you breath it repeatedly, but it is not too bad to touch)

Copper (green in electric kiln)
1 spoon copper carbonate
6 spoons dry clay

As you notice, some coloring metals are much stronger than others. These can be combined in any way you want to get other colors. Adding rutile is like adding some yellowish color.

I tell students that thick coats (several applications) of slip will look different than thin coats. They should be sure to try both approaches to see what they like better. Sometime thin coats disappear entirely under glazes. Some glazes cover more than others. Thick glazes cover more than thin glazes. By not showing an example first, they have no reason to expect a certain effect, and I tell them to expect surprises. It never fires the way you expect it to the first time. Their friends will always like it better than they do because friends do not pre-visualize the result before it if fired.

This is an example of a piece with brown slip and a light tone glaze over it. The slip was combed with an old credit card I notched with a scissors. I never buy a tool if I can make it. I often use things they were not intended to be used for. http://www.goshen.edu/~marvinpb/ex22.htm

VARIATION using wax
Paint a slip design on the leather-hard or softer piece. When the slip firms to leather-hard, cover the area with Wax Resist (available from ceramic suppliers - it is wax emulsified in water). When the wax dries, at leather-hard stage scratch additional lines, hatching, etc. Paint with a different colored slip. Give it several slip coats. Slip that is on top of the wax will rub off after firing before glazing.

How to To Make Black Slip - from Marvin Bartel

Black is tricky to make using oxides - easier with stains.

I do not use a black slip, but if I were going to make one I might start with 1 part cobalt oxide (a strong blue colorant) with 9 parts red iron oxide (a less powerful brown colorant) and 20 parts clay to make it stick to wet pots (this is not for bisque). If you want it to look black when you are using it, just add India ink or black tempera. These burn out entirely during firing.

If it is not dark enough after firing, use less clay (some clay is needed for adhesion).

If it is too blue, add iron or subtract cobalt.

If it is too brown, add cobalt or subtract iron.

You will note that these colors are opposites on the a color wheel - so it is a matter of neutralizing opposites to get black.

If you put glaze over this type of black slip, it may turn blue (this is the tricky part).

I have a good black glaze that is simply a medium dark brown glaze with 6 percent cobalt added to make it black. When I overlap or dilute it with another glaze, it turns blue. I use it for a night sky background for my dream pieces.

One part black nickel oxide with two parts clay might might also work for black slip but probably just grey. It may turn a bit green, so some red iron oxide might kill the green. This black could be combined with the cobalt and iron black to make slip that is less likely to deviate under glazes.

Using a color inclusion stain (like Mason stain), one should be able to mix black stain with just enough clay to make it stick to the wet pots. Probably 1 part black stain and 2 parts clay. Stains cost more because they are oxides that have been pref-fired with silicates and then ground back to a powder for our use. This stabilizes the color so it does not change much when we fire it. What you see is what you get.

All this is simply off the top of my head educated guesswork based on many years of working with the stuff. Please tell me what happens if you try it.

Marvin Bartel

Cleanup in clay room: http://www.goshen.edu/art/DeptPgs/clean.html
Working with clay safely:
http://www.goshen.edu/art/DeptPgs/Hazards.html