Amy Eberhardt Posted June 8, 2015 Report Share Posted June 8, 2015 I have three pieces that I've thrown over this past weekend that I intend to apply a black Terra Sigilatta to, that will ultimately be Raku fired. I understand that these pieces need to be bone dry before applying the T.S. My questions are as follows: Should I burnish them prior to the application of the T.S., or am I setting myself up for the T.S. to be more prone to flaking off in the bisque firing? If burnishing prior to the application of T.S. an acceptable step in the process, will it aid in achieving a deeper luster to the T.S., or would I just be wasting my time in doing so? Thanks in advance for any input offered on this subject. Link to comment Share on other sites More sharing options...
Dick White Posted June 8, 2015 Report Share Posted June 8, 2015 I would burnish the clay as soon as you have trimmed it at leatherhard. Then let it fully dry to bone dry. Finally, apply terra sig and buff in your usual manner. The raku clay likely has (lots of) grog for strength against thermal shock. The grog will protrude from the surface of the clay as it dries (the clay content in the clay body will shrink as it dries while the grog does not shrink) leaving a rough surface. Trying to smooth such a surface by coating it with terra sig is an exercise in futility. Success with the terra sig starts with burnishing the leatherhard clay body to push in any grog near the surface. Thus, you have a bone dry surface that is already fairly smooth. The terra sig just adds the shine. There are some who will suggest lightly sanding the piece with very fine sandpaper (and appropriate dust protection!!), but I've found for raku clay that just excavates the grog particles leaving a moonscape of craters which is just as much of a problem for the terra sig as the gravel road it was before. Link to comment Share on other sites More sharing options...
Marcia Selsor Posted June 8, 2015 Report Share Posted June 8, 2015 Dick is right. Most raku clay is full of good sized grog. You can use a smooth raku clay if you can find one. It isn't easy to burnish a piece with grog. Also why use black terra sig. Won't the smoke from raku make the TS go black? I use porcelain for pieces to which I apply TS. These are for obvara, foil saggar and ceramic saggar. Marcia Link to comment Share on other sites More sharing options...
oldlady Posted June 8, 2015 Report Share Posted June 8, 2015 what do you picture in your mind when these pots are finished? there may be another way to achieve that goal. Link to comment Share on other sites More sharing options...
Amy Eberhardt Posted June 9, 2015 Author Report Share Posted June 9, 2015 I wish that Clay Art Center in Tacoma, WA. had a picture of the two pieces I fell in love with on their website. Then everyone could see what I'm in pursuit of. The two pieces I mention were done in their Digi6 clay body with the black T.S. overlay and then bisque to ^06. The Raku glaze used is called "PacMan" and was drizzled/poured onto the bisque piece prior to Raku firing. It was very dramatic and to die for!!! **drool! drool!! drool!!** I talked with CAC's glaze and clay guy, and he saw no reason why I couldn't achieve a similar effect with the clay I already had on hand, but I picked up some of their Digi6 anyway. The three pieces I have that are drying now are made of the Georgie's G Mix I already had on hand, so this will be something of a trial run. I'm hoping to achieve a more polished finish on the T.S. surfaces that will show through the areas where the glaze is not applied and maybe compliment the glaze to a greater degree than the two sample pieces they have on display in the gallery there. It was my understanding that the artist did NOT burnish his pieces prior to bisque firing. The T.S. surface was just a slight bit rougher than I'd like to see it be, but still smoother than what would have been achievable with their stock black clay body. Also, their black clay body would not attain the depth of black color at such a low firing as I was hoping to see,[more of a dark brown] so, hence the route of the black T.S. I think it was for this same desired effect that the artist went with T.S. as well. If I could sit down with the original artist of the pieces I saw, and pick his brain for a little while, I would, but he has since moved out of the area. Nuts! I already burnished the first piece at leather hard, when I thought maybe I should ask y'all about the best course to take on this. For once, it would appear, my instincts were correct. Whew! Thank heavens! And thank y'all for your input! I so appreciate the insights from those vastly more experienced and knowledgeable than me! Thank you! Thank you! Thank you! Link to comment Share on other sites More sharing options...
alabama Posted June 9, 2015 Report Share Posted June 9, 2015 Hey, If what you're trying to do is what I think you're trying to do, I'd throw, trim, and coat with Terra Sig while leather hard. That way, The vessel and t.s. dries at the same rate. When in doubt, experiment. See ya, Alabama Link to comment Share on other sites More sharing options...
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