Introduction: Ceramic Wheel Throwing: Using Sodium Silicate to Create a Crackle Texture
In this demo, I'm going to show how to make a narrow-necked bottle with an awesome crackle pattern made by using Sodium Silicate and a blow torch. There are some crackle glazes out there which are OK but after trying them I decided I wanted something with more form, grit, and structure to it — with the added bonus that I can glaze or stain it any color I want!! So here's what I came up with — above are a few resulting examples of messing around and testing different patterns and shapes. I hope you enjoy and can use this technique to make some awesome things of your own. Please share them with me if you do, I always love seeing what great things people come up with!
Enjoy! Stay innovative and creative!!
Step 1: Get Materials
1. Butane Torch or Heat Gun — even a blow drier will do. This will dry the outside of the clay surface so that when you expand out, the clay will crackle.
2. "Ribs" — These come in many shapes, sizes, and materials (for this I use a rubber and thin steal one) They are used to compress the clay, smooth it, and shape it as you go.
3. Brush — Any ol' brush will do, no need for fancy. This we'll use to apply "Slip" and the Sodium Silicate.
4. Trimming Knives — Used to trim away excess clay at the end.
5. Sponge (small) — Generally nice to have if the piece gets goopy or you need to smooth things out.
6. Sodium Silicate — This can be found at most ceramic supply stores and online. This is a "siccative" or drying agent that will harden the layer its applied to causing it dry out and become brittle.
7. Bucket of Water — You'll need mucho agua.
8. Clay — I used about 5 lbs of Cone 10, Sleeper Porcelain for this demo. Use any clay you like however steer clear of real "Groggy" clay (lots of sand and grit). It doesn't crackle as well and for wheel throwing can be like sand paper on your hands.
9. A "Bat" — This is a removable board that attaches to the wheel-head that can be easily removed at that end so you don't have to touch your piece and risk altering its shape. Theres many types, any will do or you can just throw directly on the wheel head.
10. "Slip" — Not shown in the picture (sorry), is clay mushed and watered down. It's basically liquid clay that can be poured on things, brushed on, etc. Not too runny though. The slip I use for this looks green but will fire black.
- Note — There are things pictured that I did not end up using, it is still a good idea to have these items on hand. Depending on what I'm making at the wheel (bigger, taller, wider, etc.), these can all come in handy. I like to be prepared so I don't have to get up to find things and lose flow.
Step 2: Center the Clay
- Note: Centering is going to be a crucial skill for this project and for all wheel throwing in general. This demo is intermediate to somewhat advanced level, so if you don't know how to "center" your clay yet, no worries, there are many MANY great tutorials on YouTube and elsewhere to show you how to do this. Once you have that down, this will be a piece of cake.
My General Centering Technique for This project:
1. Toss the clay down in the center of the wheel head (figure 1), and jiggle it a little until it is firmly stuck in place.
2. Get water on your hands and the piece to lubricate it and start it-a-spinning. Use pressure from your non-dominant hand (I'm right handed so my left hand) and press the clay into your dominant hand (figure 2) which should stay steady. Squeezing the clay together like this will force the it upwards and will begin to even out all sides into wonderful-wonderful roundness.
3. To help yourself in this process, before you get started, make the clay as close to a spherical shape as you can so its nearly there before you even start the wheel turning.
4. Once the clay goes up and "cones" (figure 3) use your non-dominant hand to press it back down and toward your dominant hand (figure 4).
5. Go up and down like this until your clay "lump" is perfectly spherical or "centered" (figure 5). You should be able to rest your hand on the clay as it spins so that it doesn't move at all. Then you know you're centered and ready to roll.
Step 3: Opening Up
- Note: Many people get centering down and then when they go to open the form knock it off center. This can be insanely frustrating.
- Reasons this is happening could be:
- Being too forceful when opening
- Not finding the actual center before pressing down to open
- The most common reason is not supporting the opposing side of the wall with palm or fingers when pulling the center open toward one direction.
1. In figure 2, you can see I am supporting all sides of the form as I pull it open. My pinky is draped over the top to keep the rim in shape, and my right hand is supporting the outside of the back wall as my middle fingers on my left hand gently pull the form open.
2. Make sure to leave enough clay at the bottom for a "foot" and don't push through to the wheel head. I usually leave approx. a 1/2 or 1/4 inch. You can trim away excess later but can't add material. However try not to leave TOO much clay. You will need to compress the clay at the bottom to prevent cracking. If there is too much, that becomes more difficult.
Step 4: Pulling Up
1. "Pulling" is what gives wheel thrown objects their height before pushing out to create most objects.
2. Before pulling up, make sure the inside of the form is nicely shaped and smooth and "COMPRESSED" (to prevent cracking). As you pull the piece taller and begin to shape it, it will become increasingly difficult to reach the bottom of the inside of the piece. So now is the time to make it nice and tidy.
2. There are MANY techniques for "pulling". For the first pull, I create a ridge or indent on the inside at the bottom.
3. With the wheel spinning at medium to slow speed and my arms stable from resting them into my side, leg, or on the splash pan of the wheel (figure 1), I push inward and up from the outside using my right hand (dominant hand) (figure 1) and with the fingers on my left hand that I used to created a ridge with, I pull the clay slightly inward and upward — squeezing the clay together like this between my hands forces the clay to go upward (figure 2).
4. Keep your pulls steady and continuous (remember to breath too, i forget all the time). For this form pull almost to the top but stop and ease out of the pull with about a half inch to go (figure 6). You will need this excess clay at the top later to off the form and make the narrow neck.
5. After each pull, its important to "compress the rim" (figure 3 and figure 6). Pinch the inside and outside of the rim with one hand and press down with the index finger on your other hand to force the rim into a smooth and even shape. Doing this prevents the rim from getting all wonky at the top as you pull clay upward.
6. Repeat this pulling process until you have the desired height. I try to complete all of my pulls no matter how big I'm throwing in 3 pulls. Thats just me, I find more pulls than that and things start go astray. With this form you will need the walls to be a little thicker to stretch it outward and make the cracks, so don't over pull up and make things too thin.
7. Lastly, use a "rib" to clean up the shape and smooth things out before you apply the slip and start to make the crackle. Like you do what a "pull', be sure to support the inside of the form with one hand as you press on the outside with a rib so things don't get off center (figure 7).
Step 5: Adding Slip
1. Get out whatever color or type of slip you want to use. Take out your brush and paint away. Apply to any area you'd like to crackle...
Step 6: Applying Sodium Silicate
- Often this step and the previous step, I will merge into one. I will mix slip and some Sodium Silicate together in a batch and then apply. This speeds up the process when doing multiple objects. For demonstration sake I did these as separate steps. Either works. The mixed way, you may get a bigger, cleaner crackle pattern but to each their own, they both look great to me.
- DON'T let the Sodium Silicate drip on areas you don't want to crack. If it does, stop what you are doing, take your sponge and metal rib and scrape off any residue. If left, it could cause your piece to crack in weird places, dry unevenly, or pull your piece of center.
Step 7: Dry It Out
1. Using a blow torch or heat gun, dry the area you applied the Sodium Silicate to until it's dry to the touch. Don't dry the rest of the piece, you will still need to work with those areas.
Step 8: Pushing Out
1. Now, FINALLY, to create the crackle you will stretch the piece outward from the inside.
2. The inside will have dried a little from the blow torch stage, so be sure to put slip-water (the white slip that accumulates in your water bucket as a results from throwing NOT the different colored slip you applied with a brush) on your hands to lubricate the inside as you push outward. Try not to drip the white slip on area you want to crackle. It's fine if you do, just doesn't look as good. If you do, don't touch it, just let the whole piece dry as is when done and then use a razor blade to scrape the drip off.
3. From here on you can't touch the outside where the crackle is so be cautious of how hard and where you push to keep a nice form that has fluid and aesthetically pleasing lines.
4. The more you push out the bigger the cracks get which is great but simultaneously, the walls will become thinner and thinner. Be careful you don't go too thing so the the cracks break through to the inside of the vessel.
Step 9: Closing Off the Neck
1. This part can be tricky so slow and steady wins... Firstly you will need to use more, white, slip-water from your water bucket to lubricate the outside as you press in to create the neck of the piece.
2. Supporting the neck from all sides with your fingers (figure 1), "collar" the neck in and stat closing it off. You may need to make some some small pulls to extend the neck of the piece up and in, this where that extra clay we left at the top will come in handy.
3. As you "collar in", the lip almost always gets a little wonky. Use a sharp metal trimming knife to cut the wonk off, so it does not affect the centeredness of the rest of the piece (figure 2). I usually have to do this at least twice with skinny necked bottles like this (figure 5).
4. Once the narrows so you can't get your fingers in to support from each side as you pull up and in, use the end of a paint brush or needle tool to support the inside and then continue to pull up and in with you fingers (figure 4).
5. Once desired height is reached, trim off anything uneven (figure 5)
6. This step's not required but I like to dry out the top a bit with the torch to ensure it doesn't lose its shape when I pull it off the wheel at the end. (figure 6)
Step 10: Trim the Foot
1. Now we want to remove the excess clay at the bottom of the object and give it a nice shape. Using a trimming knife (I use a wooden one) you gently carve off sections of the bottom until you like the form. Slow the wheel down for this stage. Push down slow and steady until you feel the knife hit the bat or wheel head.
2. Using a sharper metal knife, cut down vertically through the section you just made. I cut right in front of me so you can't see me doing it in the photos. However in figure 2 I turned the wheel so you can see that downward slice facing us in the picture.
3. Then, take the sharp metal knife and cut that section you just trimmed away from the piece off of the bat or wheel head.
- Recap: Trim a section away from the piece, then make vertical cut downward like you're cutting cake. Then cut the whole coil off the bat by carving underneath.
4. Once the all the cuts are made, grab an end piece you created by making the downward cut and pull that coil off the bat and away from the piece (figure 2).
5. Repeat these steps until you have trimmed enough off and you are happy with the shape.
6. Use a metal rib to clean up the trim marks.
Step 11: Completing
1. Now pry the bat off the wheel head (I use a metal fish scaling tool I got in Japan but a knife or fork or maybe just brute strength will do) and set the piece aside to admire your beautiful crackle patterned slim-necked bottle. Or any shape you make with crackle pattern for that matter.
Voilà!! You're done!
Nice work and thanks so much for viewing. Good luck on many more successful projects!!!