1. I paid my deposit and returned my signed contract a number of weeks ago but I haven’t heard from South Cheshire Glass regarding a site survey and fit date?
Don’t worry we haven’t forgotten you, we only need to carry out the site survey a couple of weeks prior to fitting, but if you have any concerns or questions do not hesitate to give us a call on 01270 213366.


2. Are you Fensa registered?
Yes we are a certified installer, our registration number is 12394. This means that South Cheshire Glass is compliant with regulations 4 & 7 of the Building Regulations 2010.


3. Why do I need to use toughened glass and what are the benefits?
conservatoriesToughened glass is glass that has been modified by thermal treatment to give:

Strength and flexibility in accordance with BS EN 12150
Safety - up to BS EN 12600 class 1
Improved resistance to heat
High strength to weight ratio
Light transmission equal to ordinary glass
Safe to handle – sharp edges are removed
If toughened glass breaks it shatters into relatively harmless particles

The unique combination of performance characteristics listed above makes toughened glass fit a diversity of demanding applications. Overhead and low level glazing
including partitions, glazed doors, bath & shower screens, tables & trolleys, furniture, vehicles, street furniture and domestic appliances.

Toughened glass must be permanently marked to show compliance with the appropriate standard, for example:

BS EN 12150 Thermally toughened soda lime silicate safety glass
BS 857:1967 Safety glazing for land transport
BS AU 178a:1980 specification for road vehicle safety glass
BS 3193: 2008 domestic appliances

Mandatory safety glazing areas:
Approved document N of the building regulations
Workplace (Health, Safety and Welfare) Regulations 1996
Enforced under the Consumer Protection Act 1987
BS 6262 Part 4 Glazing for Buildings
BS 6180 Code of practice for protective barriers in and about buildings


4. Why have I got diamond shaped marks (spots or lines) on the glass that appear when I have condensation or in certain light, it looks as if the glass has potentially previously been leaded?
This natural phenomenon that is referred to within the glazing industry as a quench mark. Visible quench patterns are an indication that the glass has been heat treated (either heat treated or fully tempered, the patterns do not determine which). They are not a defect within the glass.

When the glass is viewed under particular lighting conditions, especially when viewed at an angle, faint diamond/spots/lines caused by the air quench process involved in the toughening process can often be seen. These marks can be seen in transmission and in reflection, and at most viewing angles other than directly facing the glass. They become very visible when polarising sunglasses are worn. They are easily seen on a sunny day when light comes from a dry blue sky or is reflected from clouds. They are less visible on grey overcast days.

The illustration below shows how the quench jets in a tempering furnace cannot cool the glass uniformly. As a result some areas are cooled faster than others resulting in differential shrinkage which creates areas of different compressive stress. When glass is stressed in the quenching operation, with its corresponding very slight changes in density, it becomes birefringent or polarising: that is it rotates the angle of the plane of polarised light. The greater the stress the greater the rotation effect will be.

Over a period of time the likelihood is that the quench marks will fade and become less visible to the naked eye.


5. I can see a mark in the glass that has been installed, what can I do about this?
Any glazing defects must be reported to South Cheshire Glass within 48 hours and we will respond accordingly to each individual case. Very rarely you may come across finger prints, smears or other dirt within a sealed double glazed unit; in these cases South Cheshire Glass will change the unit as soon as possible.

South Cheshire Glass work to the Glass and Glazing Federation guide lines for imperfections in glass and they are as follows: Sealed units provide a high standard of vision. Glass used in the manufacture of sealed units is similar to that used traditionally for single glass and therefore have a similar level of visual quality.

Visual glass inspections on sealed units for scratches on the outer panes must be carried out before any rendering, plastering or other works adjacent to the glazing takes place and as reasonably practicable after the installation has taken place. To perform a professional glass inspection on a sealed unit: Stand in the room no less than 2 metres away from the sealed unit and look directly through it (for toughened, laminated or coated glasses stand no less than 3 metres away).

Where it is not possible to stand at the correct distance, stand as far away as you can from the sealed unit. Do so in natural daylight but not directly towards the sun and with no visible moisture on the surface of the glass. Exclude a 50mm wide band around edge of the glass from the check.

Glass must be viewed at an angle of 90 degrees.
Flat transparent glass including laminated, toughened or coated glass is acceptable if the following are neither obtrusive nor bunched: Bubbles or blisters.
Fine scratches not more than 25mm long.
Minute particles.

The obtrusiveness of blemishes is judged by looking through the glass, not at it, under natural light. It must be understood that the glass used in sealed units is a processed glass and as a consequence blemishes are to be expected.

Toughened glass may show visual distortions which are accentuated by reflections in sealed units. This is a natural phenomenon not a fault.

Laminated glass may have a few more blemishes due to it being made of several layers.

Some low emissivity coatings may produce transient visual effects. In some lighting conditions the coating may look like a transparent film or produce a haze i.e. a cloudy look to the surface.

When light coloured objects such as net curtains are placed close to the glazing they may look slightly darker.


6. I’ve had new windows fitted but I still have condensation issues?
South Cheshire Glass does not guarantee against condensation of any kind other than a presence within a sealed unit.

Please note that the presence of external condensation is an indication that the glazing is thermally efficient and should not be considered detrimental. The more thermally efficient the glazing the higher the likelihood of condensation is.

The air surrounding us in our home always contains water vapour which is invisible. A typical example is the steam from a kettle, which rapidly becomes invisible; it has in fact been absorbed into the atmosphere. The warmer the air the more water vapour it can hold but there is a limit to the amount it can hold for a given temperature. When that limit is reached the air is said to be saturated. When saturated air comes into contact with a surface that is at a lower temperature than itself, the air is chilled at the point of contact and sheds its surplus water vapour on to that surface – initially in the form of a mist and if excessive eventually in the form of droplets of water.

Condensation is defined as the physical process by which a gas or vapour changes into a liquid. If the temperature of an object (e.g. grass, glass or metal) falls below what is known as “Dew Point” temperature for a given relative humidity of the surrounding air, water vapour from the atmosphere condenses into water droplets on its surface.

This Dew point varies according to the amount of water in the atmosphere and air temperature (Known as relative humidity). In humid conditions condensation occurs at higher temperatures. In cold conditions condensation occurs despite relatively low humidity. With regard to windows & doors it is the difference in temperature between the internal and external environment, and the glass that causes condensation to form.

Some examples of where water vapour comes from internally are:
Breathing: Two sleeping adults produce approximately 1 litre of moisture every 8 hours, which is absorbed as water vapour into the atmosphere.

Cooking: Steam clouds can be seen near saucepans & kettles, and then the vapour is absorbed into the atmosphere. The heat source itself can be a source of water vapour; the average gas cooker could produce approximately 1 litre of moisture per hour.

Washing Up: The vapour clouds given off by the hot water are rapidly absorbed into the atmosphere.

Bathing, laundry & wet outer clothing: These are often major sources of water vapour in the home.

Heaters: A flue less gas heater can produce 350cc of moisture per hour, paraffin heaters produce 4 litres of moisture for every 3.5 litres of fuel burned.

Indoor plants: A frequently unrecognised but nevertheless significant source of water vapour.

New property: The bricks, timber, concrete and other materials in an average 3 bedroomed house absorb about 7000 litres of water during construction. Much of this is dissipated into the indoor atmosphere during the drying out period.


7. I have had a toughened double glazed unit installed and from certain angles it appears to have faint grey narrow long lines running through it, is it faulty?
The appearance of these lines is optical phenomenon known as Brewster’s Fringes, this not a defect of the glass, and can occur with any glass of high optical and surface quality. This phenomenon is a result of the high quality now being achieved worldwide by modern methods of glass manufacture. Brewster’s Fringes occur if wavelengths of light meet up with each other when they are exactly 180º out of phase – an example of the phenomenon known to physicists as the interference of light.

The effect is similar to, although usually much smaller than the interference fringes which can sometimes be seen on toughened glass windscreens.

Brewster’s Fringes occur when the surfaces of the glass are flat and the two panes of glass are parallel to each other, i.e. when the light transmission properties of the installation are of a very high order. This phenomenon is not a defect of the product, being dependent on the laws of physics and not on the quality of the insulating glass. In fact it arises because modern glass made by the float process is flat, therefore, free of the distortion inherent in sheet glass.

The occurrence of Brewster’s Fringes is in its nature rather like the fact that under certain conditions, the observer will see a reflection of himself/herself in any window or door and no-one could claim that this was a defect of glass.

NOTE: Patterned Glass – the above criteria do not apply to patterned glass as, due to the method of manufacture, imperfections such as seeds, bubbles are deemed to be acceptable.


Quality, Style & Security Windows & Doors - Serving South Cheshire for 40 years