This video is all about clay.
Hi, new potters are you ready to get some of your clay questions answered?
Hi, Marie here with another info-packed video for you.
In today's video, I made up a list of 21 questions about clay that I've been asked
on this channel as well as my pottery crafters website from what's the difference in terms of
plasticity and elasticity in clay to why are there so many clays to choose from.
Yes, pottery clay is confusing. Follow along as I answer some of the most frequently asked beginner
clay questions. There are 21 questions in this video so if you feel like jumping around the
video for a specific answer there are timestamps down below in the description for you. Okay, let's
move on. The first question is from Art. He asks is the clay harmful or toxic to humans or pets?
Yes and no. No commercial wet clays are not toxic to humans or pets when you're working with them,
and yes clay can pose a risk if you or your pet ingest it.
Keeping your food away from your work area is always a good idea. Dry clay can also pose a
risk. Clay contains silica and clay dust can become harmful to your lungs over time. As you
can see when you buy clay it says non-toxic on the box and it gives a caution about clay dust.
Is pottery clay food safe? Yes and no. The clay has to vitrify. That's when the silica
melts into the clay particles and becomes glass-like, which forms a waterproof surface.
Some clays don't vitrify, like earthenware. High fire clays like stoneware and porcelain
can be considered food safe when fired at cone 10 - 2345 degrees Fahrenheit or 1285 degrees Celsius.
That's when the particles melt together and become vitrified. To make your clay food safe
you need to apply glaze. Just make sure the glaze label says food or dinnerware safe.
Does pottery clay stain clothes? Again yes and no. The darker clays can stain if you have minerals
such as iron oxides in them. The light-colored clays do not stain and wash right out.
If you like darker clays and you're concerned about the clay staining your clothes
you can wear an apron which is highly recommended when working with clay anyway.
Alicia asks, why are there so many clays to choose from?
That's a good question. This can be confusing to a new potter.
That's why in the beginning most teachers will keep the clay selection
pretty simple. Several factors come into play as to why there are so many clays to choose from.
You have clay bodies that are fired at different temperatures. Earthenware is
mainly a low fire clay, while stoneware and porcelain clays range from mid to high fire.
Different fluxes are added to clay, like feldspar, boron, frits, and talcs, just to name a few.
These fluxes lower the high melting temperature of silica in the clay.
Different minerals are added to the clay, like iron oxides to create different colors.
There are also many different percentages of minerals you can add to achieve many different
clay compositions which affects the workability, shrinkage level, and durability of the clay.
These are just a few reasons why there are so many clays to choose from and as your skills
grow so will your clay selection. Who knows you may even mix up your own batch of clay someday.
Alan asks what's the difference in the terms plasticity and elasticity in clay
plasticity is when the clay can be shaped and formed without returning to its original shape.
Elasticity is the opposite it's elastic. Like this rubberband. It wants to move back to its original
shape making it harder to shape and center your clay. Many porcelain clays are like that.
That's one of the reasons why they're not recommended for beginner potters.
The next question comes from Tyler. Can you pour clay wastewater down your drain?
No, the clay particles will start to stick to the pipes and will clog the pipes. You should have
a bucket for your wastewater or install a sink trap to catch the clay particles. It's totally
worth it in the long run. I left a link for the sink trap in the show notes below. Trust me you
don't want to call a plumber. Bonnie wants to know, should I get clay with or without grog?
If you're not familiar with grog it's fired clay that's ground up fine
or coarse and used to help strengthen the clay, reduce shrinkage rate, and help prevent cracking.
The use of grog would greatly depend on what you're doing with the clay.
For hand-building yes using grog helps to keep the clay stronger while you're working with it.
You will get less shrinkage and it will help prevent cracking.
For throwing on the wheel, not so much. If your hands can handle it go for it. For me, it was like
sandpaper. I couldn't do it my hands were hurting after a while. That's why I recommend Amaco 46
Buff or Amaco 38 white for throwing because they stay up pretty good for not having grog.
Should I recycle my clay or just throw my scraps away? Recycling your clay makes total sense. Why
waste? The amount of scrap clay an average potter goes through is totally worth reclaiming it.
Especially beginner potters. I have a video on an easy less messy way to recycle your bone dry clay.
There's a link for you in the show notes below
Robert wants to know can I mix different clay bodies together?
When you mix clay bodies together you're creating a new clay body
therefore you'll have to do your own testing for shrinkage and fit to the glazes
there's no way to determine beforehand if this is going to work.
That's why it's suggested that beginner potters do not mix two or more clay bodies together until
they learn the nature of clay and they're able to test fire with their own favorite glazes first.
Jessica wants to know, why do you have to wedge your clay when it comes in pre-pugged bags.
For those of you who aren't familiar with the term pre-pugged,
it's clay that's gone through the wedging machine called a pug mill before it's packaged.
Even with pre-pugged bags of clay, you can run into problems. You don't know how
long it's been in the bag and you can still get hard spots and air bubbles in the clay
if your clay isn't wedged properly. You will run into problems as you're molding your clay.
Re-wedging helps to align the clay particles
making the clay more workable. Gives you more consistent moisture throughout. And will get
rid of any air pockets that may be lurking in your clay. What's a good surface to wedge and work on?
A good surface to work on is wood. It doesn't absorb as much water and the clay doesn't stick
to the surface. And it's easy to clean. You can work and wedge on surfaces like cement granite
plaster or even canvas. The plaster can absorb too much water from the clay, and clay dust can
accumulate under canvas. These are things to be aware of when you're choosing your work surface.
The next question is from Sarah. Which clay is used to make dinnerware like plates or cups?
Dinnerware can be made from most any type of clay, but hands down stoneware clay
is the best. It's nice and plastic and it's more durable than other clays.
This one is from Simone. Can you dry your greenware clay for a few weeks
then glaze it and single fire it.
Yes, you can, but this is done more with the season potters that make their own glazes and are
skilled with the firing process of kilns. They program them properly for this type of firing.
You have to slow the rate of heat at certain times during the firing. Most commercial glazes are made
for bisque pottery. Making single firing a little more difficult. Again as your skills
grow you'll be able to make your own glaze to fit your greenware it sure is more energy efficient.
Terry wants to know how do I prevent my clay from cracking as it's drying?
There are several ways that you can prevent this. The first is to compress the clay particles
so the platelets align. If they're not aligned they look like this.
And then they separate as the clay dries.
When your clay is aligned they look like this and come together when it dries.
When throwing on the wheel you're already compressing the sides
so you just have to compress the bottom and the rim.
When hand building you need to compress and smooth out both sides of the clay
this aligns the platelets and smooths out the clay.
The second is to dry your clay out slowly and tenting is one of the best ways to do this.
Cover your clay with plastic for at least one to two days.
I do both of these things and my pottery only cracks
if I rush the process by not compressing or tenting.
If you're getting any value from this video hit the like button at any time during the video.
If you have high fire clay, can you fire it with a low fire glaze?
Yes, you can fire high fire clay at a lower temperature.
The only problem you may run into is your glaze may not fit to your clay.
The glaze needs to expand and contract with your clay. If you do it it's best to test-fire first.
Randy asks does clay expire or go bad? No, you can hold on to clay as long as you want without it
expiring. Clay can get mold on it, but you can cut away the moldy parts or you can mix it right into
your clay. If you're not allergic to mold it'll actually make your clay more plastic or workable.
What's a good way to store clay?
Good question. Use a thick plastic bag or even double or triple your bag and seal it
really tight. Make sure there are no holes, so the air doesn't get in. Then place it in a plastic
container. Like this. Storing clay like this works really well. This question is from Vicki. Can you
fire low fire clay to a higher temperature? If so how much higher can you fire it?
When you think of melting in the kiln you think of glaze. Clay can also melt in the kiln because
it contains silica Low fire clays contain fluxes that lower the melting point of the silica that's
in the clay making low fire clays more sensitive to higher temperatures. For most commercial clays
the recommended firing temperature is cone 04 - 1945 degrees Fahrenheit or 1063 degrees Celsius.
As the clay goes past the temperature it will start to bloat, then bubble,
and then melt. It's best not to fire your clay past cone 04. Especially beginners.
Sharon wants to know, how do you determine which clay to use?
There are five things you want to look for when choosing your clay. What type of clay earthenware,
stoneware, porcelain? What do you want to make decorative or dinnerware items?
Then there's texture. What do you want your clay to be? Smooth coarse or in between?
Cone size. What temperature are you, your class, or studio firing to. Color. What effect are you
looking for? Would you like your pottery to be buff, white, brown, red, or even black?
And price. What's a good price point for you? For more information, you can check out my Video or
Post on choosing your clay. I left links for you in the show notes below.
This question is from Mary Jean.
What process do you use when making a wet piece to ensure the final piece will be the size you want.
When making your piece you want to be aware of the shrinkage rate. Measuring your clay when wet
and then after the final fire will give you the most accurate measurement for future pieces. For
example if you want your mug to be six inches tall and three and a half inches across you want to
make it ten percent larger, which is a little over six and a half inches high and four inches across.
As a rule, I go for 10 percent larger when I'm crafting my clay.
Mohini asks, what happens to the clay in the kiln. As the temperature of the kiln slowly rises
the water molecules slowly evaporate. And then the chemically bonded water molecules evaporate.
Then the organic materials burn off. The clay will shrink as it bonds together permanently hardening
the clay. The heating and cooling of the clay needs to happen gradually or your piece will crack
from the pressure put on it during the process. For more detailed information on clay don't
forget to check out the links that I left for you in the show notes, and hit the like button.
Today I went through 21 beginner clay questions and hopefully cleared up
the confusion so that your next pottery making project will be a little easier.
Looking for more pottery making tip videos? You can check out these two next. 21 Brush Glazing
Tips and Beginner Kiln questions. If you do I get to play with more clay. Let's stay dirty.