Min

Appreciate the people who have shared their recipes for a clear glaze. Getting a well fitting clear is one of the harder glazes to come up with.
For those new to mixing their own glazes, be sure to test the glaze for FIT before making up a big bucket. Glaze fit to a claybody is no different than fitting a pair of jeans. What fits my body won't necessarily fit everyone else's body. If you use a high expansion glaze on one side of a pot and a low expansion one on the other there is a good chance of the pot dunting / cracking.
If someone is looking for a clear glaze to use with or over stains or underglazes or some specific colouring combinations (like chrome tin pinks, reds, purples etc) then you need a specific type of clear glaze that is hospitable to the colourants. 

Appreciate the people who have shared their recipes for a clear glaze. Getting a well fitting clear is one of the harder glazes to come up with.
For those new to mixing their own glazes, be sure to test the glaze for FIT before making up a big bucket. Glaze fit to a claybody is no different than fitting a pair of jeans. What fits my body won't necessarily fit everyone else's body. If you use a high expansion glaze on one side of a pot and a low expansion one on the other there is a good chance of the pot dunting / cracking.
If someone is looking for a clear glaze to use with or over stains or underglazes or some specific colouring combinations (like chrome tin pinks, reds, purples etc) then you need a specific type of clear glaze that is hospitable to the colourants. 

Appreciate the people who have shared their recipes for a clear glaze. Getting a well fitting clear is one of the harder glazes to come up with.
For those new to mixing their own glazes, be sure to test the glaze for FIT before making up a big bucket. Glaze fit to a claybody is no different than fitting a pair of jeans. What fits my body won't necessarily fit everyone else's body. If you use a high expansion glaze on one side of a pot and a low expansion one on the other there is a good chance of the pot dunting / cracking.
If someone is looking for a clear glaze to use with or over stains or underglazes or some specific colouring combinations (like chrome tin pinks, reds, purples etc) then you need a specific type of clear glaze that is hospitable to the colourants. 

I then layer on thicker portions to push it more and more three dimensional.  If you haven't really sculpted anything before, keep it simple so you don't get frustrated or over whelmed.  You can slowly progress more lifelike and more detailed as your skills progress.  This is great for medallions to mount on a wall as basic relief sculpture. Or you mold and cast it in ceramic to add to pottery.  I've made custom light switch plates this way, for example.  This particular one is going to be a show award for an upcoming event this spring, and another later this summer at the Kentucky Horse Park.  I plan to produce it in porcelain bisque as well as glazed. 
Right now it still needs plenty of work.  I want to soften and refine the mane and then do a lot of smoothing before I will go onto pouring a rubber master or molding.
 

A for effort Pres! Appreciate that it must be hard coming up with a new question every week.

For a large piece I would roll out a slab of the same clay as your sculpture is made from, make it about 1/4 - 3/8" thick then cut strips of it about 3/4" wide. Dry the strips between boards (or drywall pieces or whatever). When you go to fire your sculpture lay the strips down first, gaps between them, and sit your sculpture on them. (don't need to bisque fire them but make sure they are bone dry before firing and fire slowly) What you are trying to do is raise the piece off the shelf and allow air circulation underneath the piece to help even out the temperature.
Re slowing down between 1000F - 1100F both when heating and cooling, it's at approx 1060F that quartz inversion happens. As the quartz crystals change from an alpha crystal structure to a beta one there is a volume change of 1 - 2%, this can stress the clay and cause cracking / dunting. 
 

For a large piece I would roll out a slab of the same clay as your sculpture is made from, make it about 1/4 - 3/8" thick then cut strips of it about 3/4" wide. Dry the strips between boards (or drywall pieces or whatever). When you go to fire your sculpture lay the strips down first, gaps between them, and sit your sculpture on them. (don't need to bisque fire them but make sure they are bone dry before firing and fire slowly) What you are trying to do is raise the piece off the shelf and allow air circulation underneath the piece to help even out the temperature.
Re slowing down between 1000F - 1100F both when heating and cooling, it's at approx 1060F that quartz inversion happens. As the quartz crystals change from an alpha crystal structure to a beta one there is a volume change of 1 - 2%, this can stress the clay and cause cracking / dunting. 
 

Hi and welcome to the forum. 
I would look at what the slow glaze program is going at during the 1000F - 1100F range, if it's more than 50F / hour then I would slow it down during that ramp. I would also slow the kiln down during cooling during the same range and not open the kiln until it's at room temp. This is something I would be looking at doing to help equalize the temp within the kiln and doing it slowing as that is a large piece and there will be substantial differences between the 1.5" thick areas, where it sits on the shelf and thinner areas.
If you aren't sure what your glazes will do in a slow cool then I would suggest running some test pieces through the firing before your large sculptural piece. I don't know what your final cone is that you are firing to but another option would be to fire it to your target cone using the slow bisque program instead of the slow glaze program then add a slow cool. Look up your make of kiln and what the preprogrammed firing programs are and compare the two.
(I'm going to delete your duplicate post in the Chemistry section)

Hi and welcome to the forum. 
I would look at what the slow glaze program is going at during the 1000F - 1100F range, if it's more than 50F / hour then I would slow it down during that ramp. I would also slow the kiln down during cooling during the same range and not open the kiln until it's at room temp. This is something I would be looking at doing to help equalize the temp within the kiln and doing it slowing as that is a large piece and there will be substantial differences between the 1.5" thick areas, where it sits on the shelf and thinner areas.
If you aren't sure what your glazes will do in a slow cool then I would suggest running some test pieces through the firing before your large sculptural piece. I don't know what your final cone is that you are firing to but another option would be to fire it to your target cone using the slow bisque program instead of the slow glaze program then add a slow cool. Look up your make of kiln and what the preprogrammed firing programs are and compare the two.
(I'm going to delete your duplicate post in the Chemistry section)

A few examples from the net:

How to Make a Clay Cylinder - Ceramics Handbuilding for Beginners - YouTube
Making a Clay Cylinder - YouTube
... and the three-part
How I hand build clay cylinders. Part 1 Pottery ceramics techniques - YouTube
How I handbuild clay cylinders Part 2. Removing the cylinder from the former. Handbuilt ceramics - YouTube
How I handbuild clay cylinders. Part 3 Attaching the base - YouTube
... where the cylinder is worked on while on a former

Note that a suitable diameter plastic pipe makes a good former being non-absorbent, smooth &  strong.

On the left, 600g (~1.3 lbs) mug.
A normal/medium mug for me, 350g, however, as the large and extra-large ones, people pick them up, 600g is now "medium" size.
The turquoise plastic tumbler is handy as a "rounder" - the taper fits most mugs, and the shape is, strangely ideal.

It's going to be a real crap shoot trying to alter a glaze without the recipe. Which is the glaze that is giving problems, Laguna Turquoise ^10 WC554? Has the amount of reduction you are doing increased?

I mix it to a SG of 1.45 for dipping or spraying and it worked well on white clays over slip/underglaze.   I haven't tried brushing.  On brown clay, not so successful -- lots of bubbles that didn't clear (experiment in process).  
 

Once long ago Etsy was a good place for people to find your work. Now there's so much stuff on there and so much of it isn't really handmade that it's nearly impossible for your work to be found unless you have a very specific niche that people can search for. If you simply make good work that doesn't have unusual search criteria, it'll just get lost in the mix. A search for 'blue mug' will result in thousands of options. But if you have a blue mug with a mouse on it, then people can find you. Etsy works well as a shopping page that you can direct people to, though. Their interface is pretty easy to use, and everything is secure, but you may need to use social media and other means to direct people there. You'll have to math out what their fees  will cost you vs setting up your own shopping site.

Well that's a nice little bit of light bedtime reading isn't it? 
Glad I'm not the only one thinking precipitates effect calculated flux ratios. Interesting seeing the phase diagram overlaid with Stull but found it hard to decipher.

Online stores aren’t less work than doing festivals or fairs, they’re just a different kind of work. Certainly less physical labour in terms of not having a booth to set up or tear down. But you have to be good at figuring out software, taking images and promoting yourself online somehow. Some people are really good at making social media connections, some people would rather have a root canal than play games with the algorithms.
As far as my personal opinion on Shopify vs Etsy goes, they’re comparing apples to oranges. Etsy is an online marketplace, and Shopify is a website building platform like Squarespace or weebly. You don’t go to Squarespace expecting them to drive traffic to you. But I’m not of the opinion that Etsy does a stellar ob of driving traffic to a given seller, and they change their SEO requirements frequently enough that no one can really make a consistent living off of it. 
Shopify is just focused primarily on e-commerce, and has a bunch of features that let it handle shopping traffic and security built in. If you build your own website on Shopify, you pay them flat fees and you own it as long as you don’t do anything illegal and keep paying them. You’re in control of your own audience, for good or ill. You’re in charge of driving your own traffic, whether through social meda, ads, your email list, SEO or other methods.
If you open an Etsy shop, they also focus on e-commerce and transactions are secure. But ultimately, they own the platform and you are subject to how they want you to run your business. You don’t have to go too far to find the cons of using Etsy. Some of the complaints are from people who aren’t approaching selling there like running a business, but some are quite valid. The way they run their external ads is borderline usury, the requirements for things like top seller badges are unsustainable and the fee structure is unnecessarily complicated. My accountant *hated* their obtuse reporting. But the reason I left was because the traffic they drove to my site didn’t result in any conversions in a 1 year period. The customers who bought were all from my own efforts (social media and newsletter).
 

Yup.
@Suresh Sundaram, your video clip is showing mocha diffusion. If you go to the link @Hulk posted Hopper explains the process he is using. Quote below from it.
Note that Hopper used a lowfire chrome red lead glaze for the red, chrome is well know to be volitive in the kiln. To recreate that look a cadmium inclusion stain could be used in a glaze or slip to get a similar colour instead of lead and chrome but probably wouldn't get the halos.
"IN THE SOUTHWEST SERIES, THE DRY GREENWARE FORMS ARE SPRAYED WITH WHITE TERRA SIGILLATA, POLISHED WITH A SOFT CLOTH AND BRUSH DECORATED WITH A VARIETY OF BRUSHES USING BLACK-BRONZE PIGMENT. THIS IS THEN FIRED TO CONE 9 IN OXIDATION. THIS IS FOLLOWED BY PAINTING AND TRAILING WITH A CHROME RED LEAD GLAZE AND RE-FIRED TO CONE 010. ALL FIRING WITH THIS SERIES IS DONE IN AN ELECTRIC KILN IN OXIDATION.   SOUTHWEST SERIES PIECES ARE PURELY DECORATIVE AND NOT FOR FUNCTIONAL USE."    

When I enter the MC6G High Calcium Matte 2 into the EU calculator I'm not seeing excess to the eutectics of CaO even though this is coming in at 0.90 in the UMF.  I'm going to assume this glaze uses a different matting mechanism, perhaps the excess alumina and silica causing the matting or a micro rippled surface. If that's the case we need another recipe to test the theory with or reduce the silica and alumina perhaps. 

 

I'll plunk it in and see what it shows. If the EU calc shows excess silica (like I assume it would) then yes. 
edit: I'll use this recipe to play around with. (without any colourants)

Also, pound the clay out into a slab until it is close to the thickness you need, then finish off by rolling. The less rolling you can do the better. Fire it on silica sand or on a waster slab. Firing on edge may or may not work depending on the type of clay you're using, especially in the cone 5 firing. For porcelain or other bodies that fuse pretty tight it's likely to warp.

To give nuance to Peter's suggestions:
The big key is to stretch the clay in lots of directions while you're rolling it out. Will you be making the slab on a slab roller or doing it free hand? If doing it free hand you will want to use various thicknesses of wood sticks to guide you in reducing the thickness. Plop down sticks that are 1" thick and roll the slab. Then pick up the slab, turn it over, spin it 45 degrees. Then roll it with the 3/4" sticks. Pick it up, turn it over, and spin it 45 degrees again. Then plop down the 1/2" sticks, roll the slab again.
Rotating and flipping is the best way to minimize warpage on big slabs. If the clay is too wet you can sometimes stretch it too much at the corners, when you pick it up, so its best to let the clay stiffen a bit between rolls.
Firing the slab is another challenge: are the kiln shelves flat? Is it worth it to go out and buy new shelves that are perfectly flat for the project? (Sometimes it is.) All the silica in the world won't help if the kiln shelf is warped. (Yes, a bed of silica can mitigate a warped shelf but a not warped shelf is the better place to start.)
Clay intended for throwing is considered "plastic". That usually involves shrinkage. Hand building clays tend not to have so much plastic clays in them. Meaning...less shrinkage. Making a large slab is usually best with a hand building clay.
The drywall trick does work well. In place of it several sheets of newspaper, under weight of a flat piece of wood, also reduce warpage in drying.
 

Bein' curious, and settled down for a late afternoon snooze*, taking a minute to look for that...
...found a scanned version of Hopper's book. The piece is "Trifoot Plate - Southwest Series."
Searching that string, found on Hopper's blog the same/similar image, captioned thus:
"RH - TRIFOOT PLATE - SOUTHWEST SERIES.
THIS EXAMPLE SHOWS CONTROLLED LOCALIZED FUMING OF CHROMIUM RED GLAZE ON TOP OF TIN-OPACIFIED TERRA SIGILLATA"
Here: PHOENIX: BRUSHSTUFF #1 (rhrising.blogspot.com)
Sorry about the all caps, that's a direct copy/past (quotes added, of quote!).
 
*Had appointment this a.m. (6:30 !!) with the specialist for a root canal.
Yep, time for a nap!

@Christy Ann, like others have said underfiring a bisque isn't usually too big a deal but going forward if you use a "dirty" clay, like one of the dark brown bodies with lots of manganese or a red clay body, you might want to try bisque firing to cone 04. The extra bit of heat helps burn out more of the impurities as does doing a slower firing. (this helps avoid some glaze issues)
It's hard to tell how a cone 6 glaze firing is going to go based on a bisque firing. Being thoughtful about how you load the pots does help. As a general rule of thumb electric kilns will fire cooler at the top and bottom and hotter in the middle. To avoid underfiring top and bottom areas load less mass in these areas, this means taller pots therefore less shelves. If you have shallow / short pots load them in the middle of the kiln using more shelves.  
Some people like to watch cones towards the end of the firing. To do this you must use proper eye protection every time you look in the kiln. (like these ones) If your target is cone 6 then you would place 3 cones in front of the spyhole(s), cone 5 (sentinel cone) cone 6 (target cone) cone 7 (guard cone). Once you see cone 5 tip down then expect cone 6 to be down in very approximatley 20 minutes. (depends on element life and kiln size). Having the guard cone will let you know if you overfired and by how much. It can be very awkward to see cones so not everybody likes doing this, above all be careful if you do. Just need a quick look, don't sit in front of the kiln and watch them fall.
If your Amaco glazes have a recommended firing going to cone 6 then I would put the kiln on low for 2-3 hours, then medium for 2-3 hours then high until you reach cone 6. 
One thing that can make a difference in when the kiln sitter trips is how you place the cone in the sitter. If you find the kiln is underfiring (if only using the kiln sitter to shut off the kiln and not looking at the cone pack) then move the sitter cone over just a bit so the bar rests on the thinner side of the cone and the opposite for overfiring. Some people much prefer using sitter bars rather than cones so they are more consistent in how they bend and positioning doesn't matter.
Like Jeff mentioned it's also possible your sitter needs adjustment. Easy to do if that's the case, video here showing how to do so if you need it.

This guy is 2-1/2 pounds, so I suppose it started with around three pounds of clay. It feels about right. No “ballast” around the bottom. I have to say, I put some real effort into throwing eggshell thin for a long time, and like to do that in demos for beginners, to show them what’s possible, but better too thick than too thin is my vibe now. Balance. 

And then use the pots.
 
High boron in this glaze? Large amount of Gerstley Borate?