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RYLANDS POLYESTER COLOUR PASTES
The range of colour pastes is based upon pigments carefully selected for heat stability, colour fastness, high opacity and having the minimum effect upon the gel time of the resin mixtures.
A standard range of 106 opaque, polychromatic, metallic and transparent colour pastes is available plus RAL and BS5252 ranges. Rylands Polyester Colour Pastes contain highly dispersed pigments and may be readily mixed directly with the parent resin in slow mechanical mixers or by hand. Violent agitation in high speed mixers should be avoided since this causes aeration with the production of bubbles in the finished mouldings.
The amount of pigment paste required will generally be between 5 -10%, but with some colours 2 - 3%, calculated on the weight of the resin will be found to be sufficient. Less colour paste will be required to be used in the lay up resin. 3602 and 3929 black accelerated resin mix should be used in less than 24 hours to avoid cobalt absorption.
For transparent colours the amount of colour paste required can vary from 2-10% depending on the thickness of moulding and depth of colour required in order to achieve a uniform finish. With polychromatic and metallic colour pastes spray application of the gel coat is recommended, and to obtain the best results they should be backed up with white.
Metallic colours numbered 11728 and 12146 are not recommended for use where a moulded article is to be exposed to the weather.
Where mouldings are produced which are components of a larger structure care should be taken to mix sufficient colour paste and resin to complete the job and so avoid colour variations. Variations of colour between mouldings can often occur from several causes. Inaccuracy of measuring of components. Variations in catalyst and accelerator quantities in resin mixes. Considerable variations in colour can result from the incorporation of colour pastes by volume.
Care must be taken to see that the percentage of given colour paste is the same in each gel coat mix. Variations in time and temperature of cure will also affect the consistency of colours between mouldings. It has been found in practice that not only should sufficient mixed colour resin be prepared for all components of a structure at one time, but also that moulding should be laid up and cured under the same conditions of time and temperature. Certain pigments undergo a change in shade when subject to high temperature. Specially compounded pigment pastes are supplied for use with hot moulding methods and also for resin systems used in cold press moulding where colour can be affected likewise.
Following the introduction of isophthalic polyester resins an increase in colour separation has occurred. Colour separation is primarily the disturbance of the gel coat surface by “sag” prior to gelation, undetectable during moulding and often caused by resin losing viscosity immediately before gelation.
Gel coats should, therefore, be applied as evenly as possible and brushed in two directions. Colour separation bears a relationship to high humidity of the atmosphere. The elevation of temperature in a moulding shop often carries with it an increase in humidity causing moisture to condense on cold mould surfaces. The evaporation of water from release agents will also increase the humidity. Gel coats of pastel shades which contain a large proportion of white tinting colour develop colour separation more readily since white pigments most commonly used are more sensitive to moisture.
See price list for complete colour range.
Colour charts are available at a nominal charge.
Note: Some colours have colour match problems between batches.
Metal Powders
For adding to gel coats for decorative finishes and cold cast sculpture. The maximum amount of powder should be added to get the best results.
Stock powders: Iron, aluminium, bronze, copper, brass, nickel brass.
Order ref.
AOO 16750 Aluminium AOO 16754 Tin Bronze
AOO 16758 Iron AOO 16752 Brass
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