Pottery/Sanding vs Sponging
I have a different question regarding preparing my greenware prior to bisquing it. I do not have a pottery background but have gotten into making handprint plates as a home business. I use a low fire soft clay b/c this is easy for baby's hands to be pressed into. The plates are custom cut & I clean them up a lot prior to set them to dry, this minimizes the amount of sanding I have to do too. Despite this, they require a lot of cleaning up in the greenware phase, I have been sanding them with both a sanding block & a small grit (220) block/sponge. They turn out great w/ this process however I really dislike the excessive "clay dust" that comes w/ this step. I take the proper precautions, use a compressor to blow away dust & I am covered & masked as well, inspite of all this I would love a less messy approach.
Recently, my husband (who is a novice as I am) pointed out why not simply clean up with the wet sponge? When I tried it, it worked great at eliminating the lines & rough areas without any dust. I watched some UTube videos & read some stuff online that indicated that if I re-wet my greenware, by trying to smooth it too much, I might cause problems w/ the glaze adhering & hot spots (which I have no idea what they are). Something about getting rid of pores & this would be what allows the bisque to have glaze stay on.
I would love a dust free process & would prefer sponging my plates until they are smooth but I would not like to jeoperdize how well the glaze adheres to the pieces.
Any pointers, assurance or suggestions will be welcomed.
Thank you for your recent question. I have never heard of glaze adhesion problems from sponging green ware, nor have I ever experienced any problems when sponging green ware to clean it up before glazing or firing to bisque. I have been in the pottery business for 30 years and have much experience with glaze adhesion.
I do know that when re-wetting green ware, you should be careful to use a slightly damp sponge so that you do not wet the ware too much and cause it too absorb too much water, causing it to crack during drying. What I like to do is to work from the inside out and really squeeze out the sponge, which allows less water to be absorbed and causes the sponge to do the work, instead of the water.
If your piece turns dark during the cleaning process, cover it loosely with a plastic bag and let it dry completely in a cool place to allow it to dry evenly. This will prevent it from cracking. Otherwise, I see no reason why you shouldn't use this method to clean your ware. It has been used this way for centuries.
I do know however that if you handle your ware with your bare hands, you could transfer oils from your hands to the ware that may prevent glaze from adhering to the ware. Therefore, it is advised that you wash your hands well with soap and water before handling your ware, or place it on a towel and use the towel to move the ware or use utility gloves to handle the ware to prevent transferring oils.
I hope this answers your question. If you have further questions, please feel free to contact me any time. I am always at your service.
Ms. Ti Phillips
Earth Stoke 'N Fire Pottery Studio and Artist Retreat