Ceramic greenware is ‘raw’ and unfired. Therefore, it is very fragile and must be handled with care. Because it is still raw it is somewhat soft in that you can cut into it to add design and to remove its mold seam lines.
Before you can paint your ceramic piece or fire it, you will need to clean it, or remove the seam lines and blemishes.The more attention you pay at this stage of your ceramic creation, the better your final completed piece will look and the more value it will have.
There are many tools on the market to assist you with cleaning your greenware, but primarily you will need the following basic tools:
Basic clean-up tool (knife on one end, double edge spoon on other end) Sponge (silk sponges work best) Stiff round white bristled brush (size 8 works best)
Sander (recommend sanding block)
Step One: make sure your work area is clean and free of obstacles and all tools are ready. Have a small bowl of water available and a small dish or tray to set your sponge on.
Step Two: Wet your sponge and squeeze it out then set it on your dish
Step Three: Hold your greenware carefully in one hand. Imagine it to be an egg shell-hold it firmly but gently. Take the spoon end of the clean-up tool and cut crosswise through the seam lines where ever there is detail or a design line crossing the seam on your item. Create a fairly deep ‘V’ cut through the seam. Repeat these cuts throughout the entire seam line.
Step Four: After all your cuts have been made, using the spoon end, carefully scrape away the seams – scraping at an angle and using care to keep from gouging. The cuts you previously made will stop your tool from cutting away the detail and design. Use knife end to access areas where you cannot reach with the spoon.
Note: often times, you will see that some of the design is absent near the seams. There are many reasons for this, but we will save that for later discussions. You will take this opportunity to incise cuts, again with the spoon end, to continue the missing design lines. It is important you make the cuts reasonably deep and open (‘V’)
Step Five: Use the sander to clean the bottom and pour gate of your item. I recommend the ‘block’ so you can keep the bottom level. (You may also set the item on an anchored piece of fine sandpaper or sanding screen and rotate it gently to level the bottom and remove the seam lines.) The sander also helps to smooth out surfaces that are plain and have no design. Use care to apply sanding aids carefully as they will ‘eat’ the greenware and you will have distortions.
Step Six: Take the stiff bristled round brush and dip it in the water, then roll it across the sponge to remove excess. Use the brush to clean the details. Draw it through the cuts, thereby smoothing them out and blending them with the design. Use a circular motion to clean the raised areas. Use enough pressure to remove all traces of the seam, but not so much as to melt the greenware and wash away the design. Clean/rinse the brush frequently, each time rolling it across the sponge to remove excess water. You do not want to apply too much water to your item or it will melt and create drip marks and it can also create hard-spots. Squeeze out your sponge occasionally so it will not become too saturated to absorb the water.
Step Seven: Once you have attended to the details, take the sponge, rinse it in clean water and squeeze it out. Gently wipe down all the plain non-detailed areas and bottom. Use enough pressure to smooth out and remove all traces of seam. Use care to not cause sponge marks from wetting the clay too much. If you see ‘wipe’ marks, let the item dry and then use a very light touch with the damp sponge to remove them. Rinse your sponge frequently, this will help to keep from a build up of clay in the sponge which will transfer to your item creating the ‘wipe’ marks. DO NOT rub or polish your item. If it becomes shiny, you will need to sand it again or you will have a problem painting it later.
Step Eight: Examine your item and see if there are blemishes like pock marks, fingernail cuts, scrapes or other damage from the mold or casting process. These can be cleaned away with the knife, sander and sponge most frequently. If you have a tiny hole from an air bubble, you can mix a drop of water with your cleaning dust until it creates a paste. Make sure the bubble is completely open at its surface (use your knife to open it if needs be). Wet the air bubble (yes, use enough water to WET it) then fill the hole with the wet paste you made from the dust. Let it set up, it will lose its shine. and then smooth it out to blend it into your design.
You are now ready to fire your greenware, or you can paint it with underglazes before you fire it.
Please feel free to use my blog to discuss this article or any ceramic related topic.