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Freeze Warnings for slips, clay and glazes
Freeze Warning. Can't ship during winter months. No warranty
against freeze damage. Dry your head and put on your mittens. Warnings like
these abound across books and the internet yet what do they all mean?
Some of these warnings are actually old wives tales which
have been repeated from generation to generation. Other warnings have merit, yet
the reason or cause to the warning is unknown or overstated. So let's take the
time to examine how cold affects the various pottery and ceramic products sold
by Dogwood Ceramic Supply:
No Warranty against freeze damage
Technically correct, but also technically wrong. Per the published tariff of each freight carrier (USPS, UPS, FedEx as well as all LTL and TL freight companies), goods are not warranted against freeze damage... unless special protection is requested. So yes the freight companies will warrant the products... if you pay for the service. The catch is pretty simple... it ain't cheap. In reality the rates are so obnoxious that they are never published. Which should remind you of the old adage: "if you have to ask how much there will be no way you can afford it".
There is got to be a better way. There is. We (the entire ceramic industry) just blame the freight carriers and say they refuse to warrant the products against freeze damage.
Skip to Dogwood Ceramic Supply's Freeze Policy
Why is Freezing & Frozen Products an Issue?
Frozen Glazes and Decorating Products
1). Water expands during the freezing process (ice is less dense than water). This expansion is not normally a cause for concern for most color products sold by Dogwood Ceramic Supply EXCEPT the narrow mouth gallon jugs of glazes. Most glazes packaged in the narrow mouth jug have minimal excess room in the bottle and even the slightest freezing of the liquid can expand the liquid and overflow the jug or actually break the plastic jug if the lid does not give way. Other sized or packaged liquid products typically do not have this expansion problem as there is usually enough excess room in the container to accommodate the expansion of the glaze or underglaze.
2). Most of our products DO NOT freeze at 32°F. At least not freeze solid. The contaminates (what we would call the dissolved minerals, clays etc) in the products generally lower the freezing point of the water. Typically 28°F is considered the temperature trigger point to start the freezing process because of the dissolved metallic salts present in the glaze formula. However, to freeze "solid" and cause expansion issues could require temperatures of well below 0°F and even then all of the product may not completely freeze "solid".
3). 28°F may be the trigger point for some freezing processes to begin, but friction is our friend. If the product is kept moving, the heat generated by the movement (friction) of the particles can be sufficient to lower the freezing point by 20°F or more. The problem with those lower temperatures is pretty dramatic when the friction heat dissipates and the product very quickly freezes such that even wide mouth pints may lack sufficient excess volume to handle the rapid expansion of freezing water and slurry.
4). How do you know if a glaze has frozen "solid" and thawed? Massive separation of the materials in the liquid. Massive. The freezing process causes the water molecules to separate from the contaminates suspended in the liquid. The contaminates will settle leaving a water head (liquid at the top) often occupying as much as 90% of the container volume. Simply thawing the frozen water will NOT cause the contaminates to re-suspend (reconstitute) themselves.
5). Can the frozen products be reconstituted? Yes, maybe, most likely not. A small amount of frozen water is not usually an issue. How small of an amount which is possible without any problem is subject to debate. If the water readily recombines with the contaminates (glaze materials) and properly remains in suspension the glaze may be usable. Rapid settling indicates a problem with the suspending agents and is easily detected by most prudent users.
6). However, up to a point, the modern glaze formula is less prone to freezing issues than older glaze formulas due to changes in deflocculating agents which are more shelf stable and withstand wider temperature deviations PLUS the use of finer milled particles in the modern commercial glaze formula which bind better with the water molecules and prevent easy separation and freezing. Some glaze manufacturers will even "guarantee" their modern product through repeated freeze and thaw cycles. But the temperatures used by the manufacturer in their testing procedure is usually 32 or 28°F, though some limited testing has been done at 0°F. What happens below 0°F is just about anybody's guess and those temperatures may be most critical to the stability and reconstituting issue.
7). Emulsions, such as Wax Resist, latex masking products and complex decorative acrylics CAN NOT Freeze. Not negotiable, not subject to debate, don't care what your Aunt Suzy tells you different. Freezing will absolutely ruin these products as there is no practical means of reconstituting the product. The only issue is the actual freezing point of these emulsions. One product on the market will separate (freeze) as warm as 36°F while other products might be able to withstand 28°F. In the simplest terms, because of the sensitivity to temperature, these products should never be exposed to cold temperatures.
Dogwood Ceramic Supply's solution to the freezing glaze issue is to simply delay the shipment such that we can be reasonably sure the product will not normally have a reason to sit at any one freight terminal for a length of time. Considering we have little problem with glazes inbound to our facility from either Spectrum (Canada) or Duncan (California via the Rocky Mountains) our simple policy seems quite prudent. However, with regards to wax resist and other products extremely sensitive to the cold, Dogwood Ceramic Supply will simply refuse to these products with extreme sensitivity until weather conditions improve.
Frozen Slips
Read sections 1-4 above of Frozen Glazes for basic information.
Like Frozen Glazes, the product expansion in the packaging typically used for shipping small quantities of slips is a critical issue.
However, unlike commercially prepared glazes, commercial slips are a simple slurry (clay and water blended until smooth) of relatively large particle size clays with just enough deflocculant added to aid suspension without causing casting difficulties. Because the clay particles are large, the water to clay bonds tend to be weak, and it is relatively easy for the water to separate from the clay during the freezing process. This means the freezing point of liquid slip maybe much warmer comparatively than a liquid glaze.
Frozen slip can easily reconstituted IF enough mixing energy is applied to the thawed slip. IF enough mixing energy is important. Given the average studio lacks high energy mixing equipment and the quantity of slip at issue (usually a 2900 gallon truck load stuck in a snow bank) it is often impossible for a studio to handle slip which has frozen.
The good news is Friction is our Friend. Moving slip (specifically the stopping and starting of the truck carrying the product causing the load to shift ever so slightly) will readily generate enough friction heat to keep the product from ever reaching the freezing point. Just avoid the snow banks along the road and there should be no problem.
Dogwood Ceramic Supply's solution to the freezing slip issue is to delay the shipment to prevent the shipment from sitting at any one freight terminal for a length of time (such as over a long weekend) if extremely cold temperatures are expected.
Frozen Clay
Clay is Dirt and Dirt Freezes. Right?
Yes and no. While technically correct, in that clay is dirt and dirt does freeze with no problem, most commercially prepared clays are a very simple slurry (clay
and water) which is dewatered (excess or free water removed) until achieving the right consistency for usage. Raw dirt and clays are not slurries and as such any
water in the material is simply free water (water held between pores of the granules) which is free to freeze without having to separate from the dirt or
clay. Because moist clay is such a simple dewatered slurry, the water-clay bonds are very weak and when exposed to sub freezing temperatures (below 32°F) the
water can quickly separate from the clay particles.
Separating water molecules in moist clay is bad.
Of all products (with the exception of the decorating emulsions) freezing clay is actually the most likely to happen. Even more likely to freeze than casting
slips because of the deflocculants present in the casting slip help to lower the freezing point of the product. And clay is a horrible to freeze because, unless
you have your own mixer and pug mill and are willing to spend the time and energy to remix the entire batch, there is little or no practical or cost effective way to
solve a problem.
Simpler solution? Keep it moving. Friction is our Friend. A little friction goes a long way. And because of the weight of the product it is nearly impossible to
freeze an entire box, much less a pallet, of clay with the help of a little friction.
Dogwood Ceramic Supply's solution to the freezing clay issue is to delay the shipment to prevent the shipment from sitting at any one freight terminal for a length of time
(such as over a long weekend) if extremely cold temperatures are expected.
Freezing Reality
Keep it moving is our motto. Don't ship out on Thursdays and Fridays when
products might sit in a cold spot for the weekend. With a little planning ahead our freezing risk is solved.
The same simple thing can't be said for the products coming INTO Dogwood Ceramic Supply. Spectrum is in the Frozen Tundra of Toronto. Standard Clays isn't much
better being located in Pittsburgh. Duncan might be located in scenic and semi-warm Fresno but the stuff must cross the crisp clean cold air of the Rockies at some point in
order to get to us. The solution? Keep it moving. Or double up a couple orders in the warmer seasons. Simple solutions to a potentially complex problem.
So why the Screaming Freezing Warnings? Because we must. Remember, there will always be somebody, somewhere who will insist on testing the theories freezing
water. For the rest of the world we just use some common sense, understand the reasons why some products might have a problem and then work around the problem
to meet everybody's needs.
Dogwood Ceramic Supply's Freeze Policy
All small package and freight carriers refuse to warrant their shipments against freezing damage during normal transportation. As such
Dogwood Ceramic Supply can not warrant the listed products sensitive to freeze damage when the product is either shipped or transportation by the customer from our location.
However, taking some precautions can allow freeze sensitive products to be shipped during periods of extreme cold while minimizing the risk. As a general rule Dogwood Ceramic Supply will hold or delay any freeze sensitive
product if the day time high temperature at the customer's location or any freight servicing terminal between the shipping point and the customer is below
32°F OR if the goods will likely sit at any freight terminal for a period of more than 12 hours. Products with an extreme sensitivity to cold temperatures
may be held until such time that the day time low temperatures at the customer's location or any freight servicing terminal between the shipping point and the
customer does not drop below 32°F.
Please be advised, even with taking all precautions to prevent freeze damage, any product sensitive to freeze issues are sold with
risk of damage passed to the customer.
Extreme Sensitivity to Cold
Freeze Sensitive Products
Sensitive to Extremely Low Temperatures
(all products not previously listed)
(all products not previously listed)
© 2009-2010, Dogwood Ceramic Supply
Avoid the Cold and Clay Season
October 1st, every year like clockwork, we receive a telephone from a customer. Same thing happens around April 1st.
Sometimes there are the calls in the middle of July or August. And December, January and February are good for some calls as well.
What are talking about?
COLD Slips and Clays. Sometimes it is WARM Slips and Clays. But most often COLD is
the usual issue.
Think about the typical studio. Warmed in the winter to a pleasant 68 or 70°F and cooled in the summer to 72 or 74°F. This sound like your studio? How could
this be a problem, the temperatures are only 2, 4 or maybe 6°F apart at the extremes?
Stop.
Wrong. The temperatures are not 2-6°F apart, rather there could be 10 or even 15°F swing in the temperatures.
What !?!
Think about it. WARMED in the winter, COOLED in the summer. You might set your thermostat at 68°F, but does that mean your studio remains at 68°F? No, because
if the temperature remained constant there would be no reason to WARM the air. The reverse is true in the summer when you COOL to the temperature. The
temperature you warm FROM or cool FROM is the range of temperature in your studio. Depending upon the sensitivity of the thermostat and the performance of
the appliance, the temperature might need to drop several degrees from your set point before triggering the unit to warm the room and conversely the opposite in
the summer when you are trying to cool the room. Regardless of whether you are trying to warm or cool the room, the thermostat is going to shut off the flow of
temperature altered air as soon as the temperature goal is reached at the thermostat. Does the appliance shut off when the entire room has been heated or
cooled to the temperature? Nope, only when the point in the room where the thermostat is located has reached the temperature goal. Does this mean the
entire room has been heated or cooled to the desired temperature? Not hardly.
Bottom line, setting your thermostat at 68 in the winter might result in an average room temperature of below 65°F. In the summer, your thermostat at 74°F
might result in an average room temperature above 77°F. Throw in a few drafty windows and insufficient insulation and you now have a 15°F swing in room
temperature from season to season.
15°F swing in temperature in the room AND the slips or clays stored in the room.
Welcome to the world of cold slips and clays.
Why is 10 or 15°F swing in temperature a problem?
Density and viscosity. Any fluid is affected by temperature. We don't usually notice viscosity of cold water versus warm water, but slightly warmed molasses
or syrup sure flow better than cold molasses or syrup. 10 or 15°F swing in temperature is all that is needed to really increase/decrease the viscosity of
molasses. Same thing with slips. Then throw in the problem of cold plaster being less willing to absorb water than warm plaster and casting any type of slip in
the winter with just a small change in ambient temperature can be a trick. A trick new customers have yet to discover.
Moist clay has the same problem. A small change in temperature will cause the clay to be stiffer (or less stiff). These are noticeable changes that even the
most wet behind the ears beginner can notice. Of course they usually blame the clay when it really is a problem with the room temperature.
So what about October and April?
Nice weather days. Sometimes people don't even have to run their heating or cooling appliances. And suddenly NOTHING is drying right. Too fast, not fast
enough, warping, curses it must be the clay, the slab roller or the phase of the moon. How about something simpler.... the AC ain't running. When you were
heating or cooling the room there was a blast of warm/cool air flowing about the room every few minutes which helped (or hindered) your processes. Lose the air
flow and suddenly nothing works the same as before.
The reverse also happens when the heating/cooling appliance is turned on when it was previously off. Panic stricken telephone calls about things drying to fast
etc. Instead of blaming the products how about blaming the heating or cooling appliance or the lack thereof.
While we can't avoid the COLD and CLAY SEASON we can do things to minimize the impact:
Constant usage temperature 12 months of the year. Or learn to adjust with the Seasons.
Store your slip or clay in the garage or warehouse? Bring the product into the studio several days before usage. Because of the mass (weight) of the product it
may take several days to properly heat or cool the product to the average room temperature.
Buying slip or clay from Dogwood? Our warehouse is not maintained to your studio temperature. Like your slip or clay warmer or cooler? Then store the product in
your temperature controlled studio for several days before usage.
Casting molds MUST be at the same temperature as the slip to be cast in the molds. And warm molds will set up much faster than a cold mold.
Consistent air flow. Run a circulating fan all year around to keep the air flow consistent and helps to eliminate drafty/warm/cold spots in the room.
Drying racks or carts. Dogwood Ceramic Supply sells a nice drying cart for the professional studio or class room. DIYers can build their own. Consistent drying
conditions help.
© 2009-2010, Dogwood Ceramic Supply
12590 Dedeaux Road
Gulfport Mississippi, 39503
Telephone (228) 831-4848 Fax (228)
831-3111
Showroom Business Hours:
Monday, Tuesday, Friday and Saturday 10AM to 5PM
Thursday 1PM to 6PM
Closed Wednesday and Sunday
Warranty for frozen ceramic products. Why are freeze warnings important for glazes, slips and clays that might be shipped to customers?