Conversely, too much moisture can cause the lump clay to become too sticky or too wet to work with. The metal clay industry calls this over hydrated phenomenon slip or paste, and there is a use and a need for these products, but when lump clay is needed, too much moisture is problematic as well.
Watering clay soil is challenging because it does not drain water very well, and overwatering may cause plants to die. The best way to water your clay soil is to do it profoundly and infrequently while improving the soil by adding organic matter, such as shredded leaves, compost and manure.
Clay soils tend to swell or expand when they come into contact with water. Soils rich in silt or clay have the greatest swelling potential and the greatest potential for foundation damage. They can cause heave and shift, cracks, and foundation settlement, which is costly to repair.
Clay is a soil component that goes from one extreme to the other. During periods of heavy rain, clay holds a large amount of water in its small pore space between particles. Saturated clay soils hold so much water the oxygen is excluded. We often say the plant drowned out from all the rain.
Clay soil expands when it comes into contact with water and shrinks when it dries up.
As they get wet, the clay minerals absorb water molecules and expand; conversely, as they dry they shrink, leaving large voids in the soil. Swelling clays can control the behavior of virtually any type of soil if the percentage of clay is more than about 5 percent by weight.
As clay heats up the kiln, any moisture in the clay evaporates and expands rapidly. If there are small air pockets in the clay, the expanding steam goes into the gaps. This puts stress on the clay and can cause it to break or sometimes explode.
Clay becomes waterlogged easily because its small particles absorb large quantities of water. This leads clay to expand in size and become densely compacted under pressure. Very wet clay can become compacted under its own weight creating an impervious layer.
As erosion acts on the landscape, clays may be suspended in water and carried until they are deposited by sedimentation. Most sedimentary rocks contain more or less clay as, for example, shales (almost exclusively clay), limestones, and sandstones.
The amount of water in the clay affects its plasticity, or how easily it can be shaped and molded. If the clay contains too much water, it will be too soft and prone to cracking during drying and firing, while if it contains too little water, it will be difficult to work with and may result in a weaker object.
Clays consist of negatively charged aluminosilicate layers kept together by cations. The most characteristic property is their ability to adsorb water between the layers, resulting in strong repulsive forces and clay expansion.
Soil Water Holding Capacities
Loams may hold up to 0.18 inches of water per inch of soil depth, and clays may hold up to 0.17 inches of water per inch of soil depth.
Due to its compact nature, clay is slow to absorb water and absorbs the least amount of water of all six soil types.
Clay soil forms tight layers that won't allow drainage. This means that, after precipitation, drainage issues will most likely present themselves. Many building contractors will use heavy machinery that will compact the soil and break down the soil structure, destroying the air pockets that allow for drainage.
The increasing volume of water continues to push clay molecules further apart.As more and more water is added, the water layers become thick enough to act as a lubricant between adjacent clay particles, and a mass of clay becomes soft and malleable.
Wet clay is a good medium for mold growth and bacterial incubation. People with specific types of mold allergies may be affected. Shared clay in a group setting could potentially be a medium for bacteria transfer.
One of the most important things to remember when it comes to storing unfinished clay projects is that you need to keep them moist. Different clays and the size of your piece will determine how fast your clay will start to dry out. If they are not kept moist, the clay will go past the Leather Hard Stage.
Hydration occurs as clay packets absorb water and swell. Dispersion (or disaggregation) causes clay platelets to break apart and disperse into the water due to loss of attractive forces as water forces the platelets farther apart.
Once the soil is fully suspended in the water, give the bucket a few minutes to settle. The rocks fell out of suspension almost immediately, followed by the sand. What is this? The silt will take 2-5 minutes to settle down, leaving only the smallest clay particles suspended in the water.
All clays are susceptible to some shrinkage and swelling due to changes in moisture content. Those with a higher proportion of expansive clay minerals, such as smectite, are even more prone. The depth of shrinkage and swelling is contained by the zone where moisture changes are most likely to occur.
Wet clay contains a large amount of water, a minimum of 25%, actually. When clay starts to dry, water evaporates from it. As this happens, the particles of clay are drawn closer together resulting in shrinkage.
Since there is not much space between the mineral particles in clayey soil it does not drain well at all. Hence, in the rainy season, clay soils quickly become very 'sticky'.
Why does clay shrink? Clay shrinks both during the drying process and the firing process. Shrinkage in the drying process occurs due to the loss of water layers. The finer the particle size of the clay, the more water layers; hence the more shrinkage.
All potters learn early on in their careers that clay has a memory. Clay memory, or clay particle orientation that is affixed by physical/ionic properties, is what can cause ceramic warping. This is because the clay particles tend to return to their initial orientation when they begin to dry out.
Your pottery will shrink even more in the kiln. The clays with the highest shrinkage volume can crack if not dried evenly because the drying clay is pulling away from the moist clay, and that's when separation can occur.