• Contact us +370 5 246 13 48
  • Address Justiniškių g. 138, Vilnius

Mechanical strokes

Examples and descriptions of mechanical glass breaks are provided below.

It is not possible to cover the break views of all surfaces. Time after time, depending upon the type of glass, the type of load, strength and affect time, varied breakages of the surface and the break views occur. But they are very similar to the submitted samples. Due to many reasons and varied factors, it is not always possible to determine the precise and accurate reason of the glass fragmentation. In most cases, sufficient expierence of the expertise performance and even complicated laboratory research are necessary.

Delta break I

Glass view with the lines of breakage process / Beginning of breakage
Mechanic surface load – long-term – static / dynamic – double fastening
Type of glass Polished glass, rolled sheet glass, laminated glass, ornamental glass, armoured glass
Examples Long-term big snow load in the case of double or triple fastening.
Beginning The angle of the edge crack is not upright;

Transition angle not upright;

There are no angular surfaces by the glass edge;

Break centre in the edge.
Lines of process Relatively parallel to the longer edge throughout all the surface;

Direct, not angular, slightly bent lines;

The form of delta or a bowl.
End Direct lines;

Partially till the edge of glass.
Other features Possible curvilinear cracks of the surface in the load side;

As the load increases, the number of cracks also increases.

Delta break II

Glass view with the lines of breakage process / Beginning of breakage
Mechanic surface load – long-term – static / dynamic – double fastening
Type of glass Polished glass, rolled sheet glass, laminated glass, figured (ornamental) glass, armoured glass.
Examples Long-term big snow load in the case of double or triple fastening;

Huge overload on two-side shelves.
Beginning The angle of the edge crack is not upright;

Transition angle not upright;

There are no curvilinear surfaces by the glass edge;

Break centre in the edge.
Lines of process Relatively parallel to the longer edge throughout all the surface;

Direct, not angular, slightly bent lines;

The form of delta or a bowl much furcating.
End Direct lines;

Partially till the edge of glass.
Other features Possible angular cracks of the surface in the load side;

As the load increases, the number of cracks also increases.

Surface pressure break I

Glass view with the lines of breakage process / Beginning of breakage
Mechanic surface load – long-term – dynamic / static
Type of glass Polished glass, rolled sheet glass, laminated glass, figured (ornamental) glass; very often glass pack.
Examples Too big load due to the temperature, air pressure, and/or height differences between the glass packs production and installment places;

Aquarium glass of too small measurements fastened from 4 sides.
Beginning Edge crack angle in all directions, not upright;

Not visible centre of fragmentation;

Transition angle not upright;

There are no curvilinear cracks by the glass edge.
Lines of process From edge to edge, of S and arc form;

Parallel to the longer edge, often furcating;

Direct, bent, but not angular break lines.
End From the mid of the glass always till the angle or near the glass angle.
Other features Surface curvilinear fragmentations: in the convex pieces of glass (usually the sub atmospheric pressure in the gap) – external curvilinear cracks, in the convex pieces of glass (overpressure in the gap) in the side of the gap, thus it is possible to recognize whether the break occurred due to the overpressure or due to the sub atmospheric pressure;

In the single glass curvilinear cracks in the load side;

With the increasing load, the number of fragmentations also increases.

Surface pressure break II

Glass view with the lines of breakage process / Beginning of breakage
Mechanic surface load – long-term – dynamic / static
Type of glass Polished glass, rolled sheet glass, laminated glass, ornamental glass; very often glass pack.
Examples Too big load due to the temperature, air pressure, and / or height differences between the glass packs production and installment places;

Aquarium glass of too small measurements fastened from 4 sides.
Beginning Edge crack angle in all directions, not upright;

Not visible centre of fragmentation;

Transition angle not upright;

There are no angular cracks by the glass edge.
Lines of process From angle to angle, of S and arc form;

Parallel to the longer edge, often furcating;

Direct, bent, but not angular break lines.
End From the middle of the glass till the angle or near the angle of the glass.
Other features Surface curvilinear fragmentations; in the convex pieces of glass (usually the sub atmospheric pressure in the gap) external curvilinear cracks, in the convex pieces of glass (overpressure in the gap) in the side of the gap, thus it is possible to recognize whether the break occurred due to the overpressure or due to the sub atmospheric pressure;

With the increasing load, the number of fragmentations also increases;

In the single glass curvilinear cracks in the load side.

Surface pressure break III

Glass view with the lines of breakage process / Beginning of breakage
Mechanic surface load – short-term – dynamic / static – big intensity
Type of glass Polished glass, rolled sheet glass, laminated glass, ornamental glass; very often glass pack.
Examples Too big load due to the temperature, air pressure, and / or height differences between the glass packs production and installment places;

Snow avalanche from the roof;

Glass pack filling with too cold gas.
Beginning Edge crack angle in all directions, not upright; not visible centre of fragmentation;

Transition angle not upright;

There are no angular cracks by the glass edge;

From angle to angle, of arc form much furcating ;

Break lines relatively parallel to the longer edge, when there‘s a big relation of lines;

Direct, round, but not angular break lines.
Lines of process From the middle of the glass always till the angle or near the angle of the glass
End Surface curvilinear fragmentations; in the convex pieces of glass (usually the sub atmospheric pressure in the gap) – external curvilinear cracks, in the convex pieces of glass (overpressure in the gap) in the side of the gap, thus it is possible to recognize whether the break occurred due to the overpressure or due to the sub atmospheric pressure;

With the increasing load, the number of fragmentations also increases
Other features In the single glass curvilinear cracks in the load side

Surface pressure break IV (explosion fragmentation) – polished glass

Glass view with the lines of breakage process / Beginning of breakage
Mechanic surface load – short-term – dynamic – very big intensity
Type of glass Polished glass, rolled sheet glass, laminated glass, ornamental glass; also glass pack.
Examples Very big load due to the temperature, air pressure, and / or height differences between the glass packs production and installment places;

Filled too cold gas and a big gap in the glass pack;

Explosion.
Beginning Edge crack angle in all directions, not upright;

Not visible centre of fragmentation;

Transition angle not upright;

There are no curvilinear cracks by the glass edge.
Lines of process From edge to edge, of arc form;

Break scheme with cross cracks that increase towards the gap in the middle of the glass;

Direct, often round break lines
End From the middle of the glass always till the angle or near the angle of the glass.
Other features Surface curvilinear fragmentations; in the convex pieces of glass (usually the sub atmospheric pressure in the gap) – external angular cracks, in the convex pieces of glass (overpressure in the gap) in the side of the gap, thus it is possible to recognize whether the break occurred due to the overpressure or due to the sub atmospheric pressure;

With the increasing load, the number of fragmentations also increases;

In the single glass angular cracks in the load side;

In the case of explosion, angular cracks in the load side.

Surface pressure break V (explosion fragmentation) – multi-level safe glass

Glass view with the lines of breakage process / Beginning of breakage
Mechanic surface load – short-term – dynamic – very big intensity
Type of glass Laminated glass, also glass pack.
Examples Very big load due to the temperature, air pressure, and / or height differences between the glass pack production and installment places;

Filled too cold gas and a big gap in the glass pack;

Explosion.
Beginning Edge crack angle in all directions, not upright; not visible centre of fragmentation;

Transition angle not upright;

There are no curvilinear cracks by the glass edge.
Lines of process From the middle of the arc form;

No opening;

Break scheme with cross cracks that increase towards the gap in the middle of the glass;

Direct, often round break lines.
End From the middle of the glass always till the angle or near the angle of the glass.
Other features Surface curvilinear fragmentations; in the convex pieces of glass (usually the sub atmospheric pressure in the gap) – external curvilinear cracks, in the convex pieces of glass (overpressure in the gap) in the side of the gap, thus it is possible to recognize whether the break occurred due to the overpressure or due to the sub atmospheric pressure;

With the increasing load, the number of fragmentations also increases;

In the single glass curvilinear cracks in the load side;

In the case of explosion, curvilinear cracks in the load side.

Break by the decorative frame I – in the glass pack

Glass view with the lines of breakage process / Beginning of breakage
Mechanic evenly distributed load – medium dynamics + long-term – weak dynamics + short-term
Type of glass Only glass pack from polished glass, rolled sheet glass, laminated glass, ornamental glass.
Examples Too small gap between the pieces of glass when internal decorative frames are used;

Huge differences of air pressure, temperature and / or height between glass pack production and the mounting place.
Beginning Edge crack angle in all directions, not upright;

Transition angle not upright;

Usually it is impossible to attribute unambiguously.
Lines of process Always last from edge to edge;

Direct break lines, in the area of the edge often turning away from the decorative belt;

Break parallel to the decorative frame;

Often transfer of the break edges.
End Usually it is impossible to attribute unambiguously;

Direct break lines, last till the edge.
Other features Small curvilinear cracks in the middle area;

Often in the gap of the pieces of glasses;

Possible to avoid, using the single safe glass or producing with a larger gap between glasses.

Break by the decorative frame II – in the glass pack

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot or evenly distributed load – medium dynamics + short-term or long-term
Type of glass Only glass pack from polished glass, rolled sheet glass, laminated glass, ornamental glass.
Examples Too small a gap between pieces of glass, when there are internal decorative frames;

Decorative frames with strong distance points at the centre of the frame crossing;

Huge differences of the air pressure, temperature and/or height between the glass pack production and the installment place.
Beginning Edge break angle in all directions, not up-right;

Transition angle not upright;

Usually it is impossible to attribute unambiguously.
Lines of process Almost always last from edge to edge;

Direct break lines;

Break often is parallel to frames;

Often transfer of the break edges.
End Usually it is impossible to attribute unambiguously;

Direct break lines, last to the edge.
Other features Small angular cracks in the middle area;

Often in the gap of the pieces of glasses;

Possible to avoid, using the single safe glass or producing with a larger gap between glasses.

Torsion fragmentation

Glass view with the lines of breakage process / Beginning of breakage
Mechanic evenly distributed load – short-term – dynamics
Type of glass Polished glass, rolled sheet glass, laminated glass, ornamental glass.
Examples Too small thickness of glass (often in the case of double fastening);

Glass pack compression;

The rise of the window frame.
Beginning Edge crack angle in all directions, not upright;

Transition angle not upright;

Visible outlet point in the edge zone;

Possible curvilinear cracks in the break centre.
Lines of process Always last from the edge;

Direct break lines;

Short cracks;

Often reverse lines till the edge, when they are long cracks.
End Direct lines.
Other features Often surfaces of the break edges pass over each other;

Possible curvilinear cracks in the mid area;

No centre of breakage.

Jam crack

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot or evenly distributed load – short-term dynamics – long static
Type of glass Polished glass, rolled sheet glass, laminated glass, ornamental glass.
Examples Too small or wrong supporting wooden bricks, when the weight of the glass is big;

Wrong installment of the glass belt;

No respect towards the change of the glass / frame.
Beginning The edge crack angle in all directions, not upright;

Transition angle not upright;

Visible outlet point in the edge zone;

Possible angular cracks in the break centre.
Lines of process Always last till the edge;

Direct break lines;

Short cracks;

Often reverse lines till the edge, when there are long cracks.
End Direct lines.
Other features No angular cracks in the middle area.

Edge break I – polished glass

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot load – short term – small / medium intensity
Type of glass Polished glass, rolled sheet glass, laminated glass, ornamental glass.
Examples Small stones between pieces of glass;

Hit by an object;

Hammer hit on the glass belt;

Other hits or collisions.
Beginning Edge crack angle in all directions, not upright;

Transition angle is not upright;

Visible outlet point in the zone of the edge;

Possible curvilinear cracks in the break centre.
Lines of process Beam forms form the edges;

From direct to angular break lines;

Often do not last till the adjacent edge, seldom – till other edges.
End Direct lines;

In the middle of the glass or last till the glass edge.
Other features Possible curvilinear cracks by the adjacent edge.

Edge break II – partially tampered glass

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot load – shot-term – small / medium intensity
Type of glass Only partially tampered glass by DIN EN 1863
Examples Small stones between pieces of glass;

Hit by an object;

Hammer hit on the glass belt;

Other hits or collisions.
Beginning Edge crack angle in all directions, not upright;

Transition angle is not upright;

Visible outlet point in the zone of the edge;

Possible curvilinear cracks in the break centre.
Lines of process Beam forms from the edges;

From direct to winding break lines;

Last till the edge.
End Last till the edge.
Other features Often curvilinear cracks occur by the adjacent edge;

No break isles, the crack often lasts till the edge of the glass (by DIN EN 1863) and depend upon the size and thickness of the glass.

Edge break from pressure I – polished glass

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot load – short-term – small/medium intensity
Type of glass Polished glass, rolled sheet glass, laminated glass, ornamental glass.
Examples Too small supporting logs, when the glass weight is big;

Too big pressure when screwing;

Too big pressure when tightening the wooden glass belt without gasket.
Beginning Edge crack angle in all directions, not upright;

Transition angle is not upright;

There are no or very few edge curvilinear cracks;

Clear centre in the edge.
Lines of process Beam forms from the edge;

From direct to angular break lines;

Often do not last till the edge.
End Direct lines
Other features In the middle of the glass or last till the edge of the glass

Edge break from pressure II – thermally reinforced glass

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot load – short-term or long – small/medium intensity
Type of glass Only thermally reinforced glass according to DIN EN 1863
Examples Too big pressure when screwing;

Too big pressure tightening the wooden glass belt without gasket
Beginning Edge crack angle in all directions, not upright;

Transition angle is not upright;

Edge curvilinear cracks are none or few in the beginning;

Clear centre in the edge.
Lines of process Beam forms from the edge;

From a winding to angular break lines, rarely direct lines;

Always last to the edge.
End Direct lines;

In the middle of the glass or last to the edge of the glass.
Other features No break isles and the crack always lasts to the edge of the glass (according to DIN EN 1863) and depends upon the size and thickness of the glass.

Edge break from pressure III (primary breach)

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot load – short-term or long – small/medium intensity
Type of glass Polished glass, rolled sheet glass, laminated glass, ornamental glass.
Examples Primary breach having placed on the stone or metal

Primary breach, the wrong installment of the glass belt;

Small stones or metal between the glass edge and the supporting wooden brick.
Beginning Edge crack angle in all directions, not upright;

Transition angle is not upright;

Edge curvilinear cracks are of different sizes in the beginning;

Clear centre in the edge.
Lines of process Beam forms from edges;

From direct to angular break lines;

Often do not last till the edge;

In the middle there are no cracks.
End Direct lines;

In the middle of the glass or last to the glass edge.
Other features Small or large curvilinear cracks in the beginning of fragmentation.

Corner break from the hit

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot load – short-term – small/medium intensity
Type of glass Polished glass, rolled sheet glass, laminated glass, ornamental glass.
Examples Placing on the stone or metal;

Hit on the corner by the metal object;

Glass rotation/turning over the angle.
Beginning Edge crack angle in all directions, not up right;

Transition angle is not upright;

The curvilinear cracks of the edge in the beginning are of different sizes, depending upon the force of the hit;

The clear centre in the corner.
Lines of process Beam forms from the corner;

Break lines from direct to angular ones;

Often do not last till the edge.
End Direct lines;

In the middle of the glass or last till the edge.
Other features Clear curvilinear cracks in the beginning of fragmentation

Fissure of the edge from the hit

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot load – short-term – small/medium intensity
Type of glass Polished glass, rolled sheet glass, laminated glass, ornamental glass.
Examples Placing on the stone or metal;

Hit to the edge by a metal object;

Wrong usage of adjusting belts of transportation constructions.
Beginning The angle of the edge fissure in all directions, not upright;

Transference angle is not upright; the curvilinear cracks of the edge in the beginning are of different sizes, depending upon the hit force;

The clear centre in the edge.
Lines of process Beam forms from the centre;

From direct to angular fissure lines;

Often do not last to the edge.
End Direct lines
Other features At the middle of the glass or last to the edge of the glass;

Clear curvilinear cracks.

Stone throw hole I – laminated glass

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot load – short-term – large dynamics
Type of glass Only laminated glass. In the case of armoured glass – the similar situation
Examples Stone or another bullet from the sling;

Stone hit into the front windscreen of a car at high speed
Beginning Fissure centre without an opening;

Irregular rough edge;

At the side of the fling – the conical break in the glass.
Lines of process Irregular cone fissure with short beams from the fissure centre, not always regularly centrifugal.
End At the side opposite to the inlet;

A remarkably larger outlet opening.
Other features Irregular fissure in the glass;

Often small crosscut fragmentations;

Round form = upright hit;

Oval shape = diagonal hit;

Large kinetic energy = ornamental cone = acute/sharp edge;

Smaller kinetic energy = flat cone form = larger opening;

Rear fragmentations in the opposite outlet side.

Stone throw hole II – laminated glass

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot load – short-term – medium dynamics
Type of glass Only laminated glass. In the cases of armoured glass – the similar situation.
Examples Hit with a heavy thing (hammer or similar);

Cobblestone, brick throw
Beginning At the clearly visible centre
Lines of process A bulky web;

Often direct lines, fewer angular fragmentations centrifugally from the hit spot;

Break lines often last till the edge;

The glass camber at the opposite hit side.
End Direct lines at the middle of the glass or at the edge of the glass.
Other features Depending upon the size of the tossed thing and the energy of the hit, the openings of different sizes;

Often secondary cracks occur;

Often without perforation.

Stone throw hole I – polished glass

Glass view with the lines of Breakage process / Beginning of breakage
Mechanic spot load – short-term – very large dynamics
Type of glass Polished glass, ornamental glass, rolled sheet glass, all monolithic glass, armoured glass.
Examples Stone or another bullet from the sling
Beginning A small opening at the shot side;

Irregular rough edge
Lines of process Irregular hole with short fragmentations efferent from the fissure centre, not always accurately centrifugal
End The opposite shot side;

A remarkably larger outlet opening
Other features Almost round hole in the glass;

Cone with the opening to the opposite shot direction;

Smooth acute/sharp edges;

Rear small crosscut fragmentations;

Round form    = vertical hit;

Oval shape = diagonal hit;

Large kinetic energy = vertical cone = acute/sharp edge;

Smaller kinetic energy = flat cone = irregular edge

Stone throw hole II – Polished glass

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot load – short-term – medium dynamics
Type of glass Polished glass, figured glass, rolled sheet glass, all monolithic glass.
Examples Break-in with a heavy thing (hammer or similar);

Cobblestone, brick throw.
Beginning At the centre
Lines of process Irregular hole;

A very bulky web;

From direct to angular fissure lines at the centre from the hit spot;

Break lines often last till the edge.
End In the middle of the glass or at the glass edge.
Other features Depending upon the size of the tossed thing and the energy of the hit, the openings of different sizes;

Often secondary crack occur.

Shot hole I

Glass view with the lines of breakage process / Beginning of breakage
The mechanic spot load – short-term – large dynamics
Type of glass Polished glass, figured glass, rolled sheet glass, armoured glass, all non-tampered monolithic glass
Examples Pelt by guns
Beginning Gunshot side;

A small, usually round inlet opening
Lines of process A conical hole
End The opposite side of the shot;

A remarkably larger opening of outlet
Other features An almost round hole in the glass

Cone with the opening to the opposite shot side

Smooth acute/sharp edges;

Rear, small crosscut fragmentations;

Round shape = upright hit

Oval shape = diagonal hit;

Large kinetic energy = upright cone = acute/sharp edge;

Smaller kinetic energy = flat cone = irregular edge

Shot hole II – laminated glass

Glass view with the lines of breakage process / Beginning of breakage
Mechanic spot load – short-term – very large dynamics
Type of glass Laminated glass
Examples Pelt by guns
Beginning At the centre of break on the side of the shot
Lines of process a) no shot through: shattered glass around the inlet opening:

The remnants of the shot metal at the centre;

Fragmentations of a large area efferent/ of the web shape around the centre;

Depending upon the size of the bullet and energy the decreasing break from the shot side to the opposite direction.

b) shot through: shattered glass around the shot-through openingFragmentations of a large area efferent/ the web shaped around the centre;

Depending upon the bullet size and energy, the decreasing break from the shot side to the opposite direction;

Remnants of the foil, showing the location of the outlet.
End At the middle of the glass, seldom till the edge
Other features Depending upon the size of the bullet size, type and energy;

The smaller the bullet and the larger the energy, the smaller the fissure edge and the clearer shot-through;

Camber at the side of the bullet escape.

Break of tempered glass

Glass view with the lines of breakage process / Beginning of breakage
Spot load short-term and dynamic – medium / high intensity
Type of glass Only in case of tempered glass
Examples Hammer-blow by sharp end;

Shot;

Stone hit;

In case of spot fastening.
Beginning Visible centre of breakage, in the form of a spot with curvy cracks
Lines of process Net form, starting form the centre;

Typical image of single safe glass shattering; no fragments;

Cracks in the entire area.
End In the entire area, incalculable, at all edges, always up to the edge
Other features Shattering structure in the entire area;

Curvy cracks in the centre;

Not visible on single glass, as the glass falls into fragments in case of a crack.

Nickel sulfide breakage of tempered glass “Spontaneous break”

Glass view with the lines of breakage process / Beginning of breakage
Spot load – short-term – dynamic – high intensity
Type of glass Only in case of tempered glass
Examples Very rarely;

Happens during 10 years after tempering of glass;

Possible in all types of tempered glass; possible to avoid by trying to keep hot condition (>95%).
Beginning Clear structure of butterfly form in the breakage centre (approximately 1-4 cm);

Small inclusion of nickel sulfate (< 0,2 mm) as a black spot near the central line of the butterfly in the centre of the glass.
Lines of process Net form, starting form the centre;

Typical image of single safe glass shattering;

Small fragments;

Cracks in the entire area.
End In the entire area, incalculable, in all edges, always up to the edge.
Other features Shattering structure in the entire area;

No curvy cracks in the centre;

Not visible on single glass as the glass falls into fragments in case of cracking.