Table of Contents
Crazing develops when excessive tensile stress is applied to a polymer, leading to microvoid formation in a plane normal to the stress. The voids initiate at microscopic inhomogeneities in the polymer, and are stabilised by fibrils of plastically deformed polymer chains.
What is plastic crazing?
Crazing is the phenomenon that produces a network of fine cracks on the surface of a material, for example in a glaze layer. Crazing frequently precedes fracture in some glassy thermoplastic polymers. As it only takes place under tensile stress, the plane of the crazing corresponds to the stress direction.
How do you fix crazing?
Crazing in Stoneware Glazes: Treating the Causes, Not the Symptoms Apply a thinner glaze coat. Add increasing amounts of silica. Remove some feldspar and line blend additions of silica. Firing higher or over a longer time. Add increments of 5% silica to the clay body.
What is crazing caused by?
Crazing is caused by the glaze being under too much tension. This tension occurs when the glaze contracts more than the clay body during cooling. Because glazes are a very thin coating, most will pull apart or craze under very little tension.
How can we prevent plastic crazing?
Avoid overly harsh cleaning of plastic – solvents such as acetone are too aggressive and leave plastics vulnerable to stress cracking. Use the least amount of adhesive required to cover the bond area. Minimal gap and minimal adhesive reduce the cure time – thus reducing the dwell time.
What does crazing look like?
Crazing is a term used to reference fine cracks that can be found in the glaze of pottery or china. Crazing can be present in varying degrees. Sometimes items may have a couple of crazing lines on one side and not the other, other times the crazing can look like a spider web and cover the entire item.
What is the difference between cracking and crazing?
As nouns the difference between crazing and crack is that crazing is a covering of fine cracks on a hard smooth surface such as a glazed object or car exterior while crack is (senseid)a thin and usually jagged space opened in a previously solid material.
Does crazing reduce value?
The presence of crazing usually diminishes the value of objects but it can depend on the severity of the damage and rarity of the crazed piece.
Is it safe to use China with crazing?
They will turn black or brown sitting between the crazed lines or on the porcelain body itself. Nearly inaccessible, bacteria enjoy this environment. You must recognize that regardless of the method you use to clean crazed china, it is no longer food safe.
What does crazing look like on pottery?
Have you ever seen a piece of pottery where the surface looks like it’s covered with a spider web of tiny cracks? That’s called crazing. They are not cracks in the actual piece of pottery but rather surface-level cracks in the fired glazed of the piece.
Does Refiring fix crazing?
Either the body expanding or the glaze shrinking can cause fine hairline cracking (crazing) to occur. Refiring to the proper cone will sometimes solve the problem. Firing to the proper cone number is critical to help eliminate crazing problems. Witness cones must be used to verify the heatwork the ware receives.
Does crazing cause leaks?
Crazing on earthenware pots can cause them to leak, as the fired clay body remains porous and water can seep through. The cracks can also harbour dirt and bacteria, so are not ideal on functional pots.
How do you fix ceramic crazing?
In practice, the most effective ways to correct crazing are: increase the silica, in body or glaze. decrease the feldspar, in body or glaze. decrease any other material containing sodium or potassium. increase the boron. increase the alumina, i.e. the clay content. increase lead oxide.
What causes acrylic crazing?
The majority of times you see cracking and crazing in plastics such as Acrylic, Perspex, Plexiglas (PMMA), Polycarbonate (PC) and Ultem (PEI) is due to lack of the correct heat treatment. These such plastics need careful normalising and annealing steps throughout the machining, bonding and polishing process.
Does polycarbonate crack when drilled?
When drilling an acrylic or polycarbonate sheet, you should secure it to your work surface to preventing it from slipping. You should also back up the plastic piece with a scrap of plywood or MDO. The scrap sheet of material relieves any pressure on the plastic, which minimizes chipping and cracking.
What is concrete crazing?
November 9, 2018. What is Crazing? Craze cracks on concrete is when the surface of concrete develops a lot of fine cracks. Sometimes called map-cracking or alligator cracking, crazing of concrete is a result of conditions and curing methods at the point the concrete is laid or even the way it is finished.
What causes gelcoat crazing?
Crazing is caused by the gelcoat expanding and contracting over a given area. Cracked gelcoat should be removed. After gelcoat removal, sand the fiberglass laminate with 80-grit sandpaper. After sanding, make any needed repairs to the area.
What is crazing on eyeglasses?
Crazing is a web of tiny cracks that can appear on the lenses of eyeglasses coated with an anti-reflective coating. Looking through crazed lenses can make your world appear blurry. There are many benefits to getting anti-reflective coating (also called AR or “anti-glare”) on your eyeglasses.
How do you remove crazing from dishes?
Start With Soap and Water Morning Glory Antiques recommends cleaning the dishes using soap and warm water. Dawn dish soap or another soap without dyes or scents are best. Scrub the dishes with a washcloth. Do not use anything more abrasive to scrub the porcelain, like a sponge or brush, since this could damage it.
Is crazing a defect?
Industrially, crazing is considered a glaze defect due to the metal being significantly weaker than an uncrazed metal of the same type.
Why did my Dutch pour crack?
Crazing happens when the top layer of the acrylic pour painting dries faster than the underlying layer which is still wet. When this happens the top layer of the acrylic film will form a skin as it hardens and continues to stretch, and if it hardens too fast it will break.
Is crazing harmful?
Glazed ware can be a safety hazard to end users because it may leach metals into food and drink, it could harbor bacteria and it could flake of in knife-edged pieces. Crazed ceramic glazes have a network of cracks.
Does crazing effect pottery?
Crazing is the effect on pottery which causes it to have a web of tiny cracks over its surface. Although crazing is generally a surface affliction, it can weaken the integrity of your piece in time, as it is opening up the glazed piece of your pottery and thus weakening its overall structure.
What is plastic crazing?
Crazing is the phenomenon that produces a network of fine cracks on the surface of a material, for example in a glaze layer. Crazing frequently precedes fracture in some glassy thermoplastic polymers. As it only takes place under tensile stress, the plane of the crazing corresponds to the stress direction.
How do you fix crazing?
Crazing in Stoneware Glazes: Treating the Causes, Not the Symptoms Apply a thinner glaze coat. Add increasing amounts of silica. Remove some feldspar and line blend additions of silica. Firing higher or over a longer time. Add increments of 5% silica to the clay body.
What is crazing caused by?
Crazing is caused by the glaze being under too much tension. This tension occurs when the glaze contracts more than the clay body during cooling. Because glazes are a very thin coating, most will pull apart or craze under very little tension.
How can we prevent plastic crazing?
Avoid overly harsh cleaning of plastic – solvents such as acetone are too aggressive and leave plastics vulnerable to stress cracking. Use the least amount of adhesive required to cover the bond area. Minimal gap and minimal adhesive reduce the cure time – thus reducing the dwell time.
What does crazing look like?
Crazing is a term used to reference fine cracks that can be found in the glaze of pottery or china. Crazing can be present in varying degrees. Sometimes items may have a couple of crazing lines on one side and not the other, other times the crazing can look like a spider web and cover the entire item.
What is the difference between cracking and crazing?
As nouns the difference between crazing and crack is that crazing is a covering of fine cracks on a hard smooth surface such as a glazed object or car exterior while crack is (senseid)a thin and usually jagged space opened in a previously solid material.
Does crazing reduce value?
The presence of crazing usually diminishes the value of objects but it can depend on the severity of the damage and rarity of the crazed piece.
Is it safe to use China with crazing?
They will turn black or brown sitting between the crazed lines or on the porcelain body itself. Nearly inaccessible, bacteria enjoy this environment. You must recognize that regardless of the method you use to clean crazed china, it is no longer food safe.
What does crazing look like on pottery?
Have you ever seen a piece of pottery where the surface looks like it’s covered with a spider web of tiny cracks? That’s called crazing. They are not cracks in the actual piece of pottery but rather surface-level cracks in the fired glazed of the piece.
Does Refiring fix crazing?
Either the body expanding or the glaze shrinking can cause fine hairline cracking (crazing) to occur. Refiring to the proper cone will sometimes solve the problem. Firing to the proper cone number is critical to help eliminate crazing problems. Witness cones must be used to verify the heatwork the ware receives.
Does crazing cause leaks?
Crazing on earthenware pots can cause them to leak, as the fired clay body remains porous and water can seep through. The cracks can also harbour dirt and bacteria, so are not ideal on functional pots.
How do you fix ceramic crazing?
In practice, the most effective ways to correct crazing are: increase the silica, in body or glaze. decrease the feldspar, in body or glaze. decrease any other material containing sodium or potassium. increase the boron. increase the alumina, i.e. the clay content. increase lead oxide.
What causes acrylic crazing?
The majority of times you see cracking and crazing in plastics such as Acrylic, Perspex, Plexiglas (PMMA), Polycarbonate (PC) and Ultem (PEI) is due to lack of the correct heat treatment. These such plastics need careful normalising and annealing steps throughout the machining, bonding and polishing process.
Does polycarbonate crack when drilled?
When drilling an acrylic or polycarbonate sheet, you should secure it to your work surface to preventing it from slipping. You should also back up the plastic piece with a scrap of plywood or MDO. The scrap sheet of material relieves any pressure on the plastic, which minimizes chipping and cracking.
What is concrete crazing?
November 9, 2018. What is Crazing? Craze cracks on concrete is when the surface of concrete develops a lot of fine cracks. Sometimes called map-cracking or alligator cracking, crazing of concrete is a result of conditions and curing methods at the point the concrete is laid or even the way it is finished.
What causes gelcoat crazing?
Crazing is caused by the gelcoat expanding and contracting over a given area. Cracked gelcoat should be removed. After gelcoat removal, sand the fiberglass laminate with 80-grit sandpaper. After sanding, make any needed repairs to the area.
What is crazing on eyeglasses?
Crazing is a web of tiny cracks that can appear on the lenses of eyeglasses coated with an anti-reflective coating. Looking through crazed lenses can make your world appear blurry. There are many benefits to getting anti-reflective coating (also called AR or “anti-glare”) on your eyeglasses.
How do you remove crazing from dishes?
Start With Soap and Water Morning Glory Antiques recommends cleaning the dishes using soap and warm water. Dawn dish soap or another soap without dyes or scents are best. Scrub the dishes with a washcloth. Do not use anything more abrasive to scrub the porcelain, like a sponge or brush, since this could damage it.
Is crazing a defect?
Industrially, crazing is considered a glaze defect due to the metal being significantly weaker than an uncrazed metal of the same type.
