I have previously posted about how I have used a rock tumbler to make sea glass from glass wine bottles and sea pottery from pottery shards. As I noted previously, I used stage 3 grit to tumble the pottery shards. I saw something on social media where a person stated you do not need to use grit at all to tumble pottery. I decided to experiment to see if I agree.
Previously a potter who was trying to reduce her inventory of pottery very generously gave me a lot of pottery to break and use for my art. I had already tumbled several different pieces with the grit, so I used some pieces with the same glaze and tumbled them without the grit. I always tumble the pottery for about a week. Lately because the pottery shards are such different sizes, I do not use pebbles or anything else to tumble with them. Hence for this experiment, the only thing that differed was one batch was tumbled with stage 3 grit, and the other batch was tumbled without any grit. The results are below.
In each of the three photos, the pieces in the photo were glazed in similar glazes. On the left are the pottery shards that were tumbled without grit, and on the right are the pottery shards that were tumbled with stage 3 grit. The shards tumbled without grit are shinier with a more glass like glaze still visible, but the shards tumbled with grit have a more matte finish with the shininess gone. Similarly, especially with the reddish shards, the pieces tumbled without grit retain the more metallic finish that they originally had while those tumbled with the grit have lost the metallic look and to a certain degree the red glaze to just show the black undertones. Importantly, the shards that are tumbled with grit have softened edges that feel nice to touch (at least to me). Conversely, while I don’t think you would cut yourself on the shards tumbled without grit, they are not soft and have a sharp edge. I often use pottery shards in my stitching, and I am not positive if the shards tumbled without grit might eventually cut thread that is wrapped around it to hold it in place. (An example of how I use pottery on stitching can be seen on this piece.)
So do you need to use grit when tumbling pottery shards? I think the answer really depends on what you are trying to achieve by the tumbling and what is important about the final product. If a shiny and/or metallic finish is important, don’t use grit. If you prefer the matte finish, or more importantly, if you want a smooth finish without rough edges, I think grit is needed. For your own projects, you might want to experiment. Tumble without the grit first. Then if you don’t like the results, put the pieces back in the rock tumbler with grit. Happy tumbling!
Below is the short video comparing the pieces in the photos above.