Glossary

Glossary.

A brief A-Z of terms used in our industry.

Adhesion is the bond made between two dissimilar materials caused by molecular interactions between the adhesive and the surface of the substrate. The force of a molecular bond is measured in Newtons per 25mm2 and the strength can be measured using various tests such as 90o peel adhesion (See Fig.1 below).

Peel adhesion testing
Fig. 1 90o Peel adhesion test

Peel adhesion tests, where the force required to peel the media defines how strong the adhesive is are commonly used for self-adhesive vinyl and films. The results can be catergorised as:

  • Removable adhesive = <19N/25mm2. These low tack films remain easy to remove after application without leaving an adhesive residue.
  • Permanent adhesive = 20-28N/25mm2. Films with a permanent adhesive will be difficult to remove after application without leaving a residue.
  • High-tack adhesive = >29N/25mm2


Adhesion failure results in delamination of the film and adhesive from the substrate.

Adhesives come in various forms and each vinyl or film will have the right adhesive properties to match the material characteristics:

  • Hot Melt - These adhesives, as the name suggests react to heat:
    • PU hotmelt adhesives are primarily used for garment decoration films where the process of transferring the film to the material uses a heat press to activate the melting point.
    • Rubber hotmelt adhesives are an economical coating for certain single and double sided tapes. The coating process involves heating the adhesive to melting point and coating it as a hot liquid, this means that these tapes are only to be used in areas not subjected to heat and direct sunlight as this would cause the rubber adhesive to dry out, turn yellowish and become brittle.
  • UV Curable adhesives off a very high level of UV, heat and water resistance and while they have a high level of cohesion, while offering sometimes useful lower level of adhesion. UVC adhesives offer complete residue free removability.
  • Solvent based adhesives have the benefit of a high degree of transparency as well as being water and solvent resistant. This makes them suitable for wet application but they also tend to be the most expensive type due to the extraction and disposal of the solvent gases from the drying process.
  • Water based adhesives are sometimes referred to as dispersion adhesives as they are mixed with water to form an emulsion. The coating process is similar to solvent based adhesives except the water vapour released during the drying stage can simply be exhausted out of the production plant. As water based adhesives can re-emulsify when they come in to contact with moisture care has to be taken if applying wet as this can cause a slight milkiness effect.

The angle of the cutting blade is measured in o degrees. The correct blade angle depends entirely on the material being cut. Here is a general guideline:

Product Blade Angle
Standard Signmaking Vinyl 45o
Heat Transfer Flex Films 45o
Flock 60o
Reflective Vinyl 60o
Floor Laminate 60o
Sandblast Films 60o
Magnetic 60o

Calendered films are the most commonly used type by signmakers and large format printers. They start life as solid granules that are melted and compounded with heat and pressure in a mixing unit. This is then extruded, being drawn through a series of temperature controlled rollers which stretches and flattens it to a uniform thickness; typically between 70µ - 100µ. Calendered films come in two main catergories; monomeric and polymeric.

Cast films are made differently to calendered films, starting off as a liquid which is then poured onto a casting sheet before moving slowly through a set of temperature controlled ovens where the liquid evaporates leaving behind an extremely thin layer. This then gets rolled; typically to 50µ or even as thin as 30µ. Cast films have little internal tension and are dimensionally stable, so shrinkage is barely perceptible. Cast films are thinner and softer, they are highly flexible and easier to apply over 3D curved surfaces using heat. With a durability in excess of 10 years, cast vinyl offers ultimate durability.

CMYK stands for Cyan, Magenta, Yellow and Black (K stands for key as it was the black plate that was called to key plate on old printing presses) and printers lay down these colours in layers of dots (see dpi below) to produce the colour that the eye will see. This mode is used for all litho and digital printing.

cmyk colours

Cohesion is the bonding of the particles within the adhesive that holds it together, gives it internal strength and prevents it from splitting and leaving a residue.
Shear adhesion tests are ideal for measuring the cohesive properties of a bond either horizontally or vertically which is commonly used for double sided tapes (See Fig.2 below).

Shear adhesion testing
Fig. 2 Shear adhesion test

Cohesion failure results in the physical separation of the adhesive which will leave a residue.

Some plastic films with a low surface energy can be made more receptive to printing inks, coatings and adhesives by passing the material through a corona treatment process. This modifies the surface energy to improve adhesion and is done during production by converting standard electricity into high frequency power and delivering it to the surface by means of a ceramic or metal electrode over an air gap.

The cutting force value is measured in grams (gf) and depends entirely on the material being cut and the angle of the blade being used. Here is a general guideline:

Product Grams of Force Value (gf)
Standard Signmaking Vinyl 30-100
Heat Transfer Flex Films 30-100
Flock 80-160
Reflective Vinyl 100-350
Floor Laminate 100-350
Sandblast Films 100-500
Magnetic 150-600

DPI stands for Dots per Inch and refers to the amount of printed dots in an inch of the print. The larger the DPI, the higher number of dots and the clearer the print will be.

Usually, the higher the DPI, the higher quality of print and this is important for large format graphics but it is not always necessary to print at the highest DPI. If the print is small, using a high DPI may just be a waste of ink and might result in poor drying times.

This stands for 'grams per square metre' and is the weight measure for various non-adhesive flexible media such as paper, canvas and banner.

The European measurement commonly used to display the thickness of a vinyl film.  1 micron (µ) equals one thousandth of a millimetre, 0.001mm.  A typical 75µ vinyl is therefore thinner than one tenth of a mm.

The American measurement commonly used to display the thickness of a vinyl film and not to be confused with mm.  1 mil (one thousandth of an inch) equals 0.0254mm.  A typical 75µ vinyl could therefore be described a 3 mil.

Monomeric grade PVC is the most economical and least durable, best suited to interior and short-term exterior applications (4 years for Black & White, 3 years for colours) on to flat 1D and slightly curved 2D surfaces.

The monomeric plasticisers used in their production to make the film softer and more flexible have a low molecular weight which after time, slowly migrates to the surface of the film causing it to shrink and become brittle. These films are therefore not suitable for demanding exterior applications such as vehicle graphics or fascia signage as it will almost certainly start shrink back from the edges to reveal the adhesive beneath. Once this starts, any dirt in the atmosphere will quickly create a dirty grey outline around the graphics and eventually, the vinyl will begin to flake off like peeling paint.

The offset value is the distance from the centre of the blade to the cutting edge of the blade and is specified by the manufacturer of the blade. The offset determines the blade's turning radius and how it compensates for distance while turning corners.

A term used to describe how light is either blocked or passes through a vinyl or film. For our industry is can be broken down to:

  • Blockout refers to a vinyl or film with zero transparency or translucence, meaning no light will pass through the material. This makes it suitable for use to block light out on windows as well as for use on to coloured substrates to prevent any show through.
  • Opaque vinyl or film blocks out most natural light and are impossible to clearly see through (however we do find that some colours will be more opaque than others). With little or no transparency or translucence, opaque vinyl and films are the most commonly used type for signage and displays.
  • Translucent films will allow light to pass through but it would be impossible to see clearly what is on the other side. Coloured translucent vinyl and films are used for glass decoration and printable translucent films are often used for backlit signage.
  • Transparent vinyl and films allow light to pass through without interference making it easy to see through to the other side. Coloured transparent vinyl and films are used for glass and window decoration.

Polymeric grade vinyl uses polymeric plasticisers that have a more complex molecular chain meaning that they shrink back at a slower rate. This makes them more durable and with better UV and temperature resistance, suitable for longer term use outdoors on 1D and 2D surfaces (10 years for Black & White, 8 years for colours). If used on more complex curves, it is still recommended to cut and overlap seams as opposed to heating a stretching like you can a cast film (see below).

Raster images are pixel based and are best used when printing non line art images such as photographs as it is possible to include chromatic graduation and complex composition. Raster files are resolution specific meaning that they are intended to be displayed at one specific resolution. Increasing the image size will result in a loss of quality with images looking jagged and decreasing the size will result in blurry less crisp images. Raster file types include TIFF, JPEG, GIF, PNG and BMP and are also the most common type of file for displaying web graphics on screen.

Liners fall in to two catergories:

  • Paper liners are typically a base kraft paper of between 90gsm - 140gsm that has either a clay coating which is commonly seen on sign making vinyl and stencil films or a PE coating which is more common on digital print media due to the higher level of moisture resistance. The coatings work as a receptive layer for the final layer which is the siliconisation.
  • For those materials requiring a final high degree of transparency, the kraft paper is replaced with a clear PET film and with a PE coating as this is much smoother.

RGB stands for Red, Green and Blue and represents colours of light that is viewable on a screen or monitor making it perfect for use on website and digital advertising.

If a graphic file is sent to print using RGB colour mode it will look very different that if it was sent over in CMYK format. This is because the printer has to change the image to CMYK to be able to process it correctly so it is always recommended that when sending artwork to print that it is done in CMYK mode.

rgb colours

There are two factors that will determine how strong the adhesive needs to be to stick to a particular surface. These are the finish of the surface and the surface energy.

  • Basically, the smoother the surface, the easier it is to stick to, simply because there is a greater surface area contact. A textured surface therefore requires a higher stronger adhesive as there is less surface for the adhesive to stick to.
  • Without getting too nerdy, surface energy is the measurement of how well an adhesive will stick to it. Every surface has an 'energy' and this is measured in 'dyne'. Basically, the higher the surface energy, the easier it will be to stick to. Imagine a newly waxed car bonnet. Rain water will bead and run off easily because the wax is creating a low surface energy so water cannot stick to it.

    Glass has a high surface energy so is easy to stick to whereas polypropylene has a low surface energy so harder to stick to and requires high tack adhesive levels to acheive a bond.

Tack refers to the initial stickiness of the adhesive and indicates how quickly a bond is formed when brought into contact with the substrate. There are various factors than can influence initial tack such as the surface energy of the substrate and temperature.

Vector images are based on mathematical formula that define geometric curves, circle, polygons and lines. Because of this vector graphics are best used for line art graphics such as logos, icons, charts and text. They are much more versatile than raster graphics and flexible so that graphics can be resized indefinitely without the loss of quality. Vector file types include EPS, AI, PDF & SVG.


If you would like to add to or can suggest any changes to these pages please feel free to contact us

Call us on 01858 431642 , we're always happy to help!

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