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Technical Tips: Next 10

Cutting out the background on a photo

White backgrounds are used for presentation on ecommerce websites (contextual backgrounds when showing a product in use). Even if you can photograph to pure white at the edges of a photo, it will transition to grey around the object and pieces will almost always have some fuzzy edges. While there are automated edge-detection tools in editors like Photoshop or GIMP, they do not give clean edges like this. So professionals do this job using a vector-editing tool. In the past this implied learning the path tool (e.g. inPhotoshop) but now inexpensive phone apps can do it well. On the lower left is the original image (already cropped). On the lower right I have it open in an iOS app named Exacto. The blue dots are stationary anchors and the black ones pull out curves between them (curves flow smoothly through the black ones). By zooming and add/moving dots I can produce these crisp edges (Exacto saves it to iOS Photos with a transparent background). Notice how clearly the clean edges enhance the throwing rings on the right.

Monday 20th January 2020

New dealer showroom clay sample boards almost ready (not available retail)

We have new boards for high temperature oxidation and reduction, medium temperature and low temperature. These feature QRCodes for each of the bodies (they go to the information pages for that product on our website, these pages are getting more and more detailed with how-to information). Each body is shown with two glazes. Those glazes have QRCodes at the bottom that will take you to a page with everything you need to know about how to use and get or mix them.

Friday 20th December 2019

Hand-tooling a mug model vs. 3D-printing a mold to cast it

I am creating molds for a 2019 casting-jiggering project to reproduce heavy stoneware mugs manufactured here 50 years ago. I have a profile drawing I want to match (upper left). The solid plaster model on the left was my first attempt at manual tooling. The metal template was time-consuming to hand-make, its contour was difficult-to-match to the drawing and the plaster surface turned out rough and difficult-to-smooth. To make the plaster model on the right I printed a shell (using my 3D printer), poured the plaster in, extracted it after set and then smoothed it on the wheel using a metal rib and trimming tool. It matches the drawing perfectly and the round is very true. 3D-printing is revolutionary for this type of thing! The drawings: I hired someone on Upwork.com to make them for me (using Fusion 360). The shell-mold (to cast the model) on the upper right: I printed that too, in two pieces.

Friday 13th December 2019

Laguna B-Mix on Steroids: Wedge in some Plainsman Fire-Red!

Both pieces have a transparent glaze, G1947U. The Fire-Red (a blend of Plainsman A1/M2 and St. Rose Red) was mixed as a slurry, dewatered to plastic form and then wedged in to the B-Mix (left piece has 10%, the other 20%, the bar in front shows the pure material). The A1 supplies most of the speckle, the St Rose and M2 impart the color. This addition does not affect the working properties of BMix (it still throws very well). An added benefit is that pieces dry better. Fired strength and maturity are minimally affected (porosity stays around 1%). With a 20% addition the surface of the unglazed clay is almost metallic. Silky matte glazes, like g2571a, are stunning on a body like this.

Thursday 5th December 2019

Cooling rate drastically affects the appearance of this glaze

This is G2934Y satin matte with Mason 6600 black stain. The piece on the left was fired using a slow-cool firing schedule (C6DHSC). The schedule for the one on the right turned the kiln off at 2100F (after a half hour drop-from-2200F-and-hold), then it free-fell. The slow cool gives the glaze on the left time to crystallize, thus it is no longer a satin matte. It is interesting that to this mix of the glaze I added 20% glossy clear, yet it still matted on the slow cool.

Tuesday 26th November 2019

What we see in the park beside the Plainsman plant

The Plainsman Clays factory is right beside a baseball park. A beautiful place in the summer where children play and teams compete. But in the afternoon and evenings the deer move in. And mow the grass! The deer stay around all winter, in this residential area they are away from the coyotes and occasional mountain lion in the nearby river valleys.

Sunday 24th November 2019

A gunmetal glaze I have wanted my whole life!

After 40+ years of making pottery I finally have a perfect gunmetal black. It has an incredible silky glaze. It does not cutlery mark. It does not craze on anything. It is easy to clean. This is G2934Y with 6% Mason 6600 black stain firing using the PLC6DS schedule. I had to tune it a bit, adding about 15% glossy G2926B, because it was a little too matte on initial firings. But now it is perfect. These are heavy mugs made using the M340 casting recipe (and the casting-jiggering process). The speckled mug was made by casting a thin layer of the speckled version of the slip first, then filling the mold with the regular slip. I used a 40-minute cast to get walls nice and thick!

Sunday 24th November 2019

This is how much casting slip 10,000 grams of powder makes

To-the-brim the bucket holds 8.8 liters (2.43 Canadian gal, 1.9 US gal). The slip itself weighs 14 kg (30 lb). It has a specific gravity of between 1.75 and 1.8. The slurry was power-mixed in a larger bucket.

Friday 22nd November 2019

Deep, deep blue without any cobalt. How?

These have to be seen to be believed, it is the deepest, richest blue we have ever produced. This is Plainsman M340 fired to cone 6. Black-firing L3954B engobe (having 10% Burnt (not raw) Umber instead of the normal 10% Zircopax) was applied inside and partway down the outsides (at the stiff leather hard stage). The incising was done after the engobe dried enough to be able to handle the piece. The glaze is Alberta Slip rutile blue. Firing schedule: Cone 6 drop-and-soak.

Wednesday 20th November 2019

The matteness of this glaze depends on the cooling rate

This is the G2934Y matte cone 6 recipe with a red stain (Mason 6021). The one on the left was fired using the C6DHSC slow-cool schedule. The one on the right was fired using the drop-and-soak PLC6DS schedule. The only difference in the two schedules is what happens after 2100F on the way down (the slow-cool drops at 150F/hr and the other free-falls). For this glaze, the fast cool is much better, producing a silky pleasant surface rather than a dry matte.

Wednesday 20th November 2019

Find thousands more like the following: Use the search field at the top of the page at the Digitalfire Reference Library.

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