Wednesday, January 19, 2011

Sprigs 101

A sprig is a thin slab or small stamped piece that is attached to the surface of a pot. I am using this method to attached a company logo to some mugs I am making for a coffee shop. It's an easy way to add surface decoration to a piece.

The first thing I had to do was order a stamp. The shop owner emailed a jpeg image of his logo to me, and I resized it and ordered a rubber stamp online. There a about a million online vendors that make custom rubber stamps, and most can do it in less than 2 days, plus shipping time. I ordered this one with 2 day express shipping since I'm on a time crunch. I placed the order on Tuesday and got the stamp on Thursday. Total cost was about $26 with shipping. The stamp itself was under $10. Not a bad investment considering I could end up making a couple thousand dollars worth of pots with it over the next couple of years.

The only issue I have with this stamp is that they trimmed the rubber too close to the logo. I would have preferred that they leave the rubber untrimmed, all the way out to the edge of the wood block. Next time I'll have to specify that when I place the order. The problem with it being trimmed to close is that if you stamp too deeply into the clay, the trimmed edge will leave an impression, and it's a lot more difficult to wipe it out when it's that close to the logo.

To make the sprig, I first roll out a very thin slab of clay, using 2 small metal rods to maintain thickness. 

To use this method of rolling even slabs, just let the rolling pin roll on top of the rods until the clay is down to that thickness. I typically use wood strips for thicker slabs, but metal rods work best for super thin slabs like this. These rods are 3/32" thick, which is the thinnest I can consistently make a successful sprig. I've tried 1/16" thick, but the slabs tear too easily. These rods are actually stainless steel mandrels for making lampworked beads, but you can pick up thin steel, aluminum or brass rods at any hardware store.

After rolling the slab I dust it with corn starch to keep the stamp from sticking to the clay, and then stamp as many times as possible, covering the entire slab. The corn starch will burn away in the bisque firing.

I then cut out the sprigs and set them on a cardboard tube to firm up. To prevent cracking and warping on the pot, the sprigs should be on the soft side of leather hard when applied, and applied to a pot of the same moisture level. By drying on the cardboard tube, they can firm up with a curve to match the curve of the mugs they will be applied to.

I then apply the sprigs with deflocculated slip. I do not score the pot or the sprig, because the slip will do the job just fine. For those of you not familiar with deflocculated slip, I'll do a post in the next few days explaining how to make it. Then I clean up the edges of the sprig and cover the pot with plastic overnight to let the moisture levels of the pot and sprig equalize.

When I glaze these mugs, I'll wipe down the sprig with a flat sponge after dipping the glaze, leaving the glaze in the recessed areas. I'll post photos when I get some finished.

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