What Kind Of Plaster Do You Use For A Wedging Table?
What is a Wedging Table?
A wedging table is a work surface used in pottery and ceramics to prepare clay. The purpose of a wedging table is to evenly mix and distribute moisture throughout the clay body through a process called “wedging.”
Wedging clay by hand can be physically demanding. Using a wedging table makes the process easier on the potter’s body. The wedging table’s smooth, non-porous surface also prevents the clay from sticking while being worked. The table allows the clay to be pressed, folded, and squeezed repeatedly to blend the moisture and remove air pockets.
Having a well-wedged clay is important for creating high quality handbuilt or wheel thrown pottery and ceramics. Evenly mixed clay with no air pockets will be smooth, consistent, and less prone to cracking or exploding during firing. A sturdy wedging table provides the ideal surface for properly preparing clay.
Types of Plaster for Wedging Tables
There are a few common types of plaster that are well-suited for creating a wedging table surface:
Hydrocal – This is a gypsum cement that is commonly used for pottery and sculpture. It is an ultra-hard plaster that provides a very smooth, durable surface for wedging clay. Hydrocal sets up quickly and is easy to mix. It can be prone to chipping on the edges if not sealed properly.
Ultracal – Similar to Hydrocal, this is another hard gypsum cement plaster. It is a good choice when you need extra strength and hardness for the wedging table. Ultracal has high compressive strength and abrasion resistance.
Pottery Plaster – There are various plaster products specifically formulated for pottery work. These are finer than standard plaster and create an extremely smooth surface when cast. Pottery plaster is easy to mix to a creamy consistency and sets up faster than standard plaster.
Dental Plaster – Used for dental molds, this plaster creates a very dense, durable, and chip-resistant surface. It can be more expensive than other pottery plasters but provides an excellent wedging table surface.
Forton MG – This is a mineral-based composite plaster system that is lightweight, strong, and resistant to abrasion. It creates a smooth surface and can be reinforced with fiberglass for extra durability.
Properties of Plaster for Wedging
When selecting plaster for a wedging table, it’s important to consider properties like absorbency, durability, and smoothness. The right plaster will allow the clay to release easily without sticking or tearing.
Absorbency: The plaster must be porous enough to absorb moisture from the clay. This prevents the clay from becoming too wet and sticky against the table surface. However, too much absorbency can quickly dry out the clay. Look for a plaster with a balanced level of absorbency.
Durability: A wedging table sees a lot of use, so the plaster needs to stand up to repeated wedging sessions over time. It should be dense and hard enough to resist scratches, gouges, and abrasion from clay particles. Durability also depends on proper sealing and maintenance.
Smoothness: The plaster must provide an ultra-smooth surface. Any texture or roughness will transfer to the clay. The plaster should be mixed and poured to create a uniform, glassy finish once hardened and polished. Smoothness allows the clay to slide easily without catching.
Preparing the Wedging Table Surface
Properly preparing the surface is crucial for creating a smooth and durable wedging table. Here are the key steps:
Sand the Surface – Use coarse 60-80 grit sandpaper to sand the table surface smooth. Sand with the grain direction to avoid scratches. Finish by sanding lightly with 120-150 grit paper. Remove all dust with a dry cloth or vacuum.
Seal the Wood – Apply 1-2 coats of sealant like polyurethane, shellac or lacquer. Let the sealant dry fully between coats per the manufacturer’s directions. Sealing prevents moisture damage and allows for easy clean up after plastering.
Apply Release Agent – Once the sealant has dried, apply a thin layer of release agent like wax, petroleum jelly or even plastic wrap. This prevents the plaster from sticking and enables easy plaster removal later.
Level Uneven Areas – Use wood putty or spackle to fill any holes, cracks or uneven areas in the table surface. Allow putty to dry fully before sanding smooth.
With proper surface prep, you’ll have a smooth wedging table ready for plaster application and years of artistry.
Mixing the Plaster
Mixing the plaster is a crucial step in creating a smooth, durable wedging table surface. Here are some tips for properly mixing plaster for a wedging table:
Use a ratio of 2 parts plaster to 1 part water. A common recipe is 2 cups plaster to 1 cup water. The exact ratio can vary slightly based on the specific type of plaster used.
Always add the plaster to the water when mixing, not the other way around. Adding water to plaster will result in lumps. Pour the measured water into a mixing container first, then gradually add the plaster while mixing.
Use a mixing tool like a power drill with a paint mixing paddle to thoroughly incorporate the plaster and water. Mix for 2-3 minutes until the plaster is completely dissolved and the mixture is smooth and lump-free.
Only mix as much plaster as can be used in 45-60 minutes. Plaster will begin to set and harden past this time frame. Prepare in small batches as needed.
Have all tools and materials ready before mixing the plaster. This includes clean water, measuring cups, mixing bucket, mixing tool, etc. Once mixed, work quickly to pour the plaster and spread it across the wedging table surface.
Wear gloves and eye protection when mixing. Use caution to avoid splashing or spurting of wet plaster.
Pouring and Spreading the Plaster
Once the plaster is mixed thoroughly, it’s time to pour and spread it evenly across the wedging table surface. Here are some tips for getting an even coat:
Pour the plaster slowly and steadily in ribbons back and forth across the surface. Avoid dumping it all in one spot. Spreading it out gradually helps prevent lumps and bubbles.
Use a plaster trowel, drywall knife, or similar long straight edge tool to spread the plaster. Apply even pressure and work in smooth strokes. Spread from the pour lines outward until you have an even layer.
Aim for a thickness of around 1/4 inch to 3/8 inch. Too thin and it may crack. Too thick and it will take longer to cure and dry.
Work methodically and deliberately. Plaster begins setting up in around 10-15 minutes, so move at a steady pace. But don’t rush – moving too fast can trap air bubbles.
After spreading, let the plaster sit undisturbed until semi-firm. Test with a finger – if it leaves an indent, give it more time. This helps avoid leaving trowel marks or disturbing the smoothness.
Once firm enough, you can lightly skim over the surface to smooth out any imperfections. Then let it fully set up before sealing or using the wedging table.
Smoothing and Polishing
After the plaster has been poured and spread evenly over the wedging table surface, it needs to be smoothed and polished in order to create an ideal working surface. Here are some techniques for smoothing and polishing the plaster:
Once the plaster has begun to set, but is still somewhat soft, use a float trowel to gently smooth the surface. Work the float in a figure-8 motion to blend any ridges or trowel marks. Apply light, even pressure as you work. Too much pressure can pull the plaster up. Use water sparingly on the surface to help smooth and close pores.
For polishing, switch to a steel trowel once the plaster has firmed up, but is still able to be scraped. Work the steel trowel in circular motions, scraping off any high spots or blemishes. Dip the trowel in water occasionally to help lubricate the surface and fill pores. Continue polishing until the surface is smooth, uniform, and has a matte sheen.
For extra polishing, use a rubbing stone once the plaster has hardened. Rub the stone in a circular motion across the surface. This will help compact the plaster and bring extra smoothness and shine. Wipe excess dust off with a clean, dry cloth. The plaster should now have a polished finish, ready for sealing.
Sealing and Protecting
Sealing your plaster wedging table is an important final step to ensure it lasts for years to come. After all the hard work of preparing the plaster and creating a smooth surface, you’ll want to protect it from moisture, stains, and other damage.
Applying a sealant will create a protective barrier on top of the plaster. This prevents water and liquids from soaking in, which could cause erosion or cracking over time. It also makes the surface less porous, limiting stains from ink, clay residue, and more.
The best sealants recommended for plaster wedging tables are:
- Polyurethane
- Acrylic
- Epoxy resin
- Wax-based finishes
Polyurethane forms a hard, durable coating that stands up well to heavy use. Acrylic sealers are easy to apply and fast drying. Epoxy resin provides a glossy, watertight seal. Wax finishes give a soft luster while allowing the plaster to breathe.
Be sure to pick a non-toxic sealer if using your wedging table for food preparation. Read the product instructions carefully and apply the proper number of coats for maximum protection. With the right sealing, your wedging table can stay looking great for many years of crafting.
Maintaining the Wedging Table
Proper maintenance is crucial for keeping your wedging table in good condition for years of use. Here are some tips for maintaining and caring for your plaster wedging table:
Cleaning
Regular cleaning keeps your wedging table looking fresh and removes any dried plaster residue. Clean the surface at least once a week with a damp sponge or cloth. Use a mild detergent or plaster cleaner if needed to remove stuck-on bits of plaster. Avoid abrasive scrubbers or cleaners that could scratch the plaster surface.
Re-Sealing
Over time, the protective sealant on your wedging table can wear away. Re-apply a thin layer of food-safe sealant every 6-12 months to waterproof and protect the surface. Choose a sealant specifically formulated for plaster or concrete. Before re-sealing, thoroughly clean and dry the table.
Repairing Cracks
Check periodically for any hairline cracks or chips that may develop in the plaster. Fill small flaws with a thin plaster slurry, allowing it to dry completely. For larger cracks or damages, you may need to re-pour that section of the wedging table with new plaster. Sand down uneven patches to smooth and blend repairs.
Safety Precautions
When working with plaster, it’s important to take safety precautions to protect your health. Here are some key things to keep in mind:
Ventilation
Plaster can release dust and chemical fumes, so it’s important to work in a well-ventilated area. Open windows and use fans to circulate fresh air. If possible, work outdoors to allow maximum airflow. Wearing a protective mask rated for dust and chemicals is also recommended.
Personal Protective Equipment
Wear safety goggles to protect your eyes from plaster splashes. You may also want to wear gloves and long sleeves to prevent skin irritation. An apron can help keep your clothing clean. Be sure to wear a mask as mentioned above.
Disposal of Waste
Let leftover plaster fully harden and cure before disposal. Break up large pieces to fit in the trash. Plaster is non-toxic but should not be poured down drains where it could clog pipes. Wipe up spills while wet and allow rags to fully dry before disposal to prevent fire hazard.
Following basic safety measures will help ensure working with plaster for your wedging table is a comfortable, hazard-free process. Pay close attention to ventilation, protective gear, and proper cleanup and disposal.
