Before any paint is made the raw materials used to make the various components of paint are tested. Specifications must be met to ensure quality and reproducibility. Some of these tests may include: For Resins: 1) Colour, viscosity, acid value, solids content. For Pigments: 2) Colour, particle size, surface are, purity. For Solvents: 3) Flash point, boiling point, specific gravity. As can be seen from the above tests, they are all measuring different properties. During the millbase stage the fineness of the particles is measured with a fineness gauge which consists of a steel base with a graduated groove onto which a paint sample is placed and spread with a Doctor blade over the graduations of 5 to 60 microns and the point at which 'pepperiness' ends is an indication of the particle size. Wet colour can also be checked at this stage, but because drying changes the colour, it will need to be checked for Colour in the appropriate resin when dry also. The following is a list of some of the standard test methods used for testing paint in the Refinish laboratory. A) BULK PROPERTIES OF WET PAINT Test Method Appropriate Standard 1) Viscosity BSB4 BS 3900 A6 2) Viscosity DIN4 DIN 53211 3) Viscosity Ford ASTM D1020 h) Brookfield D2196 5) Cone and Plate P.V.M. 64 6) Rotothinner P.V.M. 64 7) Fineness of Grind Internal 8) Density BS 3900 A12 9) Solids Content BS 3900 B2 10) Flash Point ISO 3679 11) Colour of Clearcoat Internal 12) Storage Settlement Internal 13) Skinning Internal 1“) Wet Colour P.V.M. 28 15) Pot Life 2 Packs Internal 16} Combustibility BS 3900 A11 No’s 1-6 all measure viscosity, which allow for difference thickness of 7 material and different shear rates Of the particular test apparatus 888“, DIN4 and Ford are all flow cup methods. Attached at the back is a copy of the British Standard for 8884 which shows the scope of the test method. Brookfield, cone and plate and Rotothinner all immerse an electrically driven revolving disc into a paint sample and measure the resistance (caused by the paint sample) to the rotation of the disc. 7. The fineness of grind has been described earlier. It has an internal 101 standard, again, a copy of which is attached at the back of this block. 8. Density or specific gravity is a measure of weight of a substance in grams divided by its volume in millimetres. 9. Solid content is a measure of the volatile solids of the paint. A sample is weighed, baked in an oven until all volatile material has evaporated, reweighed and the amount of material remaining is expressed as a percentage of the starting material. 10. Flash point is the minimum temperature to which a product must be heated for the vapours emitted to ignite momentarily in the presence of a flame. 11. Colour of clearcoat. This is an internal standard comparing one sample to that standard. 12. Storage settlement is a means of assessing the settling properties of paint. This may involve storage at higher temperatures to speed up settlement or centrifugal spinning to accelerate settlement and comparing results with known standards. l3. Skinning, as the name suggests, tests the paints properties in forming a paint skin in the can and also whilst drying. 14. Wet colour compares a wet sample of paint to a wet standard kept for that purpose. 15. Pot life of two packs measures the viscosity rise of activated two pack paints and determines the time at which they are no longer considered suitable for application. 16. Combustibility is a measure of the wet paints properties in supporting combustion, the temperature at which it may spontaneously combust. B) APPLICATION PROPERTIES There are few test methods for application properties. The application having a lot to do with its feel, its ease of use and so on. Different products require different application techniques and equipment, so a lot of paint's application properties are designed to work with particular pieces of equipment. Test Method Standard 1) Cratering Internal 2) Bumping Internal 3) Sagging and Solvent Pop Internal 4) Block Spread Internal 5) Film Thickness Internal 1) The Cratering Test involves the application of a thin film of paint onto a flat surface like glass, normally with a spreader and looking for craters or silicone marks. 2) Bumping involves placing a panel of wet paint in an environment where extremely fine particles (like pollen dust) can contaminate the paint surface and then baking and comparing the results with a standard. 3) Sagging and Solvent Popping are measured by increasing film thickness onto a test panel in a wedge fashion by increasing the number of coats of paint, baking at appropriate cycle and measuring the film thickness at which sagging and bumping occur. 4) Block Spread is a device which has an accurately machined bridge so that a sample of paint can be drawn down over a glass or steel test panel to have a known standard film thickness. This is often used to produce constant film thickness for other paint tests. 5) Film Thickness can be measured by several methods: a) Metallic substrates can use magnetic resistance (e.g. elcometer and pencil gauge). b) By removal of a sample of paint and measuring with micrometer or Vernier gauge. c) Whilst wet the paint can be measured with a wheel or tooth gauge which indicates the thickness of wet paint. The film thickness of paint is probably one of the most important factors in determining the physical characteristics of the paint. ‘Too little and the durability properties reduce, too much paint and the mechanical properties reduce. C) OPTICAL PROPERTIES OF FILM Test Method Appropriate Standard 1) Gloss BS 3900/D5 2) D.O.I. (Ford or Dorigon) Internal 3) Appearance Internal H) Dry Colour Internal 5) Aluminium Orientation Azimet 6) Opacity Internal 7) Transparency Internal 8) Hue and Strength PUM 25 1) Gloss is measured with an apparatus which contains a light source and a detector source and is calibrated with a known standard. The gloss may be measured at 20“ 60° and 85° to the light source. 2) D.O.I. is a measure of 'Degree of Image' clarity. This device uses a series of patterns which get progressively smaller and the observer views the painted panel reflection in order to determine image clarity. This is a more scientific way than the painters technique of reading his watch backwards by the reflection in the paint job. It is worth pointing out that image clarity is very much associated with colour, dark colours having a higher image clarity than light colours with the same level of gloss. 3&4) Appearance and Dry Colour involve assessing test pieces against standards. 5) Aluminium Orientation is measured by the Azimet test. As this implies, it measures the orientation of aluminium plates. If you assume each plate to be a mirror, then by measuring the scattering of light from these mirrors determines what angles the mirrors are at. 6) Opacity is measured by spraying a wedge coat onto a steel panel containing a strip of Morris chart (black and white pattern). The opacity is the number of coats or film thickness required to completely obliterate the Morris chart pattern. 7) Transparency can be measured by shining a light source of known strength through a paint sample and measuring the light absorbed for a known thickness of sample. 8) Hue and Strength are the measurements of colour and concentration of pigment samples and are measured by making known dilutions and comparing against standards. D) DRYING PROPERTIESZMECHANICAL PROPERTIES Test Method Appropriate Standard 1) Dust Free 2) Tack Free 3) Print Free 4) Tape Marking 5) Hardness Konig 6) Hardness Pencil 7) Hardness Knoop 8) Adhesion - Crosshatch 9) Stonechip - Nuts 10) Stonechip - Balls 11) Falling Dart 12) Erichsen Cupping 13) Mandrel 14) G - Cycle 15) Slip 16) Flatting and Sanding 1) Dust Free time is the time taken for the paint to dry sufficiently for a small amount of flock (fibrous material like dried lawn mowings), when ped onto the paint surface, to be blown off or lightly brushed off without sticking. 2,3,4) Tack Free, Print Free are the times taken for the paint to be touchable with the back of a hand and not to show a thumb print from a thumb pressed onto it. Tape Marking is the time taken for the paint not to leave a masking tape mark when masking tape has been stuck to the paint and left for a known time. 5) Konig Hardness relies on the fact that the harder a surface is, the longer a pendulum balancing on a ball on that surface will swing and the softer surfaces will swing fewer times. 6) Pencil Hardness relies on the fact that pencil leads are made with a hardness range of H10 through HB to B10. If the pencil is held at 45% and pushed away from you, the harder pencils will mark the paint with a definite indentation line where the softer pencils will not mark the paint when the graphite is wiped away. 7) Hardness Knoop - This apparatus has a hard diamond shaped tip. A known weight presses the diamond shape into the paint surface, the softer the paint the greater the penetration. The degree of penetration is measured with a travelling microscope measuring the width of the diamond. 8) Adhesion Crosshatch - In this test a scalpel is used to cut the paint down to the substrate with 10 parallel cuts in one direction and 10 parallel cuts at right angles to the first using a template. Non-release sellotape is then stuck and rubbed onto the cut area, then removed with a sharp movement. The number of squares removed is expressed as a percentage crosshatch adhesion. 9.10) Stonechip Nuts and Balls is a test to indicate the paint's abilities to withstand stonechipping. 250 grams of 3/8 nuts or 3/8 ball bearings are ped fifteen feet down a 2 inch pipe onto the test 1’ panel, which is placed underneath at ”5% to the pipe. The panel is compared against a standard. Nuts with sharp corners are more aggressive than balls. 11) Falling Dart is another adhesion test where a known shaped dart is ped onto a panel surface. The height and weight may be changed and the adhesion of paint is Checked by comparison to known standards. 12) Erichsen Cupping - This test involves a steel ball being pushed into the back of the panel until the paint on the surface cracks. This measures the adhesion during deformation. 13) Mandrel Test involves bending a painted test panel around a Mandrel with a constant taper, the pointed end having a diameter of 1/8 inch with the thicker end at 1 inch diameter. The radius at which the paint cracks can be determined. 14) 'G' - Cycle Test is a test which exposes a test panel to extremes of temperature. It cycles from -5°C to +30°C every 2% hours, representing the extremes of our weather temperature range. Paint falls when it cracks after a number of cycles. Thermal cracking is a test similar to ’G’ - Cycle using a variation of temperature and time cycles. 15) Slip is a measurement of surface slip and involves placing a known weight onto a panel. increasing the angle of the panel until the weight slips off and the angle measured. 16) Flatting and Sanding involves flatting with wet and dry papers of known grit for about 50 rubs at known time intervals and after checking the paper for any pick-up of flatted materials. the point at which no material sticks is when it is suitable for flatting. E) RESISTANCE PROPERTIES Test Method Appropriate Standard 1) Solvent Spotting BS 3900 G5 2) Solvent Rubbing Internal 3) Water Spotting BS 3900 G5 4) Water Soak SMMT 57 5) Water Spray C.W.S. 6) Humidity QCT Internal 7) Humidity Constant BS 3900 F9 8) Corrosion Salt Spray ASTM B117 9) Corrosion UDA Internal 10) Weathering Guide Internal 11) Weather-O-Meter ASTM G26 12) Q.U.V. ASTM 053-84 13) Emmaqua Internal 14) Designation of Degree of Blistering ASTM D714 1) Solvent Spotting involves putting s of solvent onto the test panel, covering the s with a watch glass and allowing to stand for the required time. The spots are wiped off and assessed for their effect. Similar tests are carried out for other possible sources of contamination on paint finishes. 2) Solvent Rubbing is a test for fully cured paint systems and involves fifty rubs with a clean cloth wetted in acetone or suitable solvent. A fully cross-linked paint system will show almost no colour removal and no softening of the paint film where a poorly hardened system will show considerable colour removal and a softened cheesy paint film. 3,4,5) Water Spotting Soak and Spray are tests which expose the paint film to water and to assess whether any changes occur with time. Water soak will also show the paint's resistance to blistering. 6.7) Humidity Testing involves paint samples being placed in an enclosed environment where the humidity level is very high. This is often achieved by using warm temperatures and is of particular relevance to the paint system's resistance to humidity blistering. 8,9) Corrosion Resistance is a measure of time of how well a paint system resists the onset of corrosion from a paint sample having had a cut mark through the paint to the steel panel, being placed in a closed environment with a continuous mist of salt solution of 12% at an increased temperature. The panel fails when rust has reached 3mm. This test again representing the harshest environment likely to occur when you park your car on an African beach with a salt spray blowing after the paint has been scratched. 10,11) Weathering Guide, Weather-O-Meter. Q.U.V. and Emagqua ae all tests which simulate accelerated weathering conditions. The Q.U.V. is probably the harshest test exposing the panel to a high level of U.V. energy. one thousand hours Q.Ufly. (41 days), being equivalent to one year Florida exposure. Emmaqua being a machine on which panels are placed. the machine aims the panels towards the sun and tracks the sun during the day. Weathering of paint systems and pigment is also carried out by exposure at sites in Florida and Stowmarket in order to get real data on paints and pigments resistance to weathering breakdown. 14) Degree of Blistering is a means to categorise both the size of blistering and the frequency of blistering. This is achieved by reference to standard photographs. As can be seen from these tests. they are designed to measure the paints performance when used by our customers! some of_which will be assessing our products all the time, others will take them for granted. F APPENDIX EQUIVALENT VISCOSITY READINGS BSBS4 FORD 4 DIN4 17 15 14 19 16 15 20 17 16 22 19 17 24 21 19 26 22 20 28 24 22 30 26 23 33 28 25 36 31 27 38 33 28 39 34 29