Working with Resin

There is considerable advice online about working with resin, but the following information and guidance we find to be especially relevant to the high quality resin we produce, and is only given with this resin in mind. (This is not to say the advice will not be helpful for other resins and other applications also, more that it is only given in respect of our products).

The Working with Resin page covers the following areas:

STORAGE OF RESIN KITS

• Avoid wrapping a cab shell, or any other large thin casting, tightly in bubble wrap. Wrap it loosely to prevent distortion.
• Ensure that no other item or piece of packaging puts pressure, however light, on the cab roof. Resin can change shape over time if pressure is applied.
• Try to avoid storing a resin kit in a loft or an uninsulated space, where possible. Those spaces can become incredibly hot in summertime and as resin is heat sensitive, it can rapidly change shape if overheated. This problem is compounded if the item is tightly wrapped or has pressure applied from packaging or other boxes.
• Avoid storing resin in a cardboard box in damp conditions. The packaging chips and materials are often bio-degradable and will rot if wet. The box may collapse under the weight of other boxes stored on top. (There may also be decals and other moisture sensitive items in the box with the kit.)
• Once you have built your model try to avoid storing it under any of the conditions mentioned above. Also, avoid displaying your finished model in direct sunlight (especially in a glass display case) or above fireplaces or heating radiators.

CLEANING

It is certainly no secret that working with resin can be more difficult than using HIPS or ABS plastic kit parts. But with care and a little patience a far more unique and interesting model can be the end result with resin. We would advise that resin parts are thoroughly cleaned of any release agent by gently washing all areas with a rich solution of warm (not too hot) soapy water (using a soft tooth brush with neat washing up liquid is ideal for this purpose) and allowed to dry naturally on some paper towel or tea-towel, ensuring the surface is flat that they are drying on. Ordinary white spirit can be used for removing release agent, though this should be used sparingly, and only if you come across more stubborn areas. We advise that Cellulose thinners are not used.

Lightly flatting parts back with a fine wet`n`dry paper can also help to prevent any potential `fisheye` paint problems if there are any significant stubborn areas. Flatting also provides a much better paint finish and a good key for primers (though the resin and metal are of high quality, and take many primers very well without the need to carry out this process.)

Another option which we have found to be effective for cleaning and flatting resin (or plastic also) is to lightly scrub the parts with Vim or Ajax bathroom scouring powder. It must be the powder form though rather than the cream version. Simply wet the model, sprinkle on the Ajax and scrub with a soft tooth brush, rinse under the tap. The result is a clean matt finish surface ready to accept a primer.

RESHAPING

Resin is very heat sensitive, as mentioned above, so try to use very hot water or a hair dryer when you need to reshape a distorted part. Slight distortion of resin parts when demoulding or during storage or transit is quite common and can easily be corrected by immersing the distorted part in hot water for a few seconds, re-shaping as required by hand and then immersing in cold water to `fix` the new shape. The hotter the water and the thinner the part the quicker a part will soften, bear this in mind on thin items such as wings or cab panels.

This process of shaping parts, can also be used for bending or curving resin parts that you want to be in an alternative shape – for example for curling up resin tow ropes. Just ensure to take care not to try to bend the resin unless it has just been removed from hot water, or has had a hair dryer focused on it.

GLUING

Resin can be sanded, sawn, drilled, filled and filed as required but a face mask should always be worn during these operations, avoid breathing in resin dust. Superglue or a fast curing epoxy resin should be used when attaching resin to resin, resin to metal or resin to plastic. Ordinary liquid poly cements (plastic glues) will not work with resin or white metal components. It is also a good idea to lightly sand the mating surfaces when attaching resin to other resin, metal or plastic parts where it is possible to do so.

PAINTING RESIN

Resin is a very versatile modelling medium that will accept any form of paint topcoat, but it is vital to use the correct primer and undercoat to begin with. For best results on both resin and plastic parts use an auto acrylic primer first. The Halfords or Hycote standard grey or white primers are ideal. (There is no need to use the Halfords Plastic Primer.) Be aware that when attaching finishing parts, such as mirrors and lights, on top of pre-painted surfaces, superglue will often dissolve some paints, especially auto acrylics. The below outlines some guidance from our experience on paint types.

A) ENAMELS
An enamel based primer will generally only accept an enamel topcoat, and anything else will attack the enamel primer. Likewise, if you apply an auto acrylic or a cellulose finish over an enamel topcoat finish this will also affect the enamel. It is however, generally safe to apply enamel on top of any auto acrylic or cellulose paint. When applying a second coat of a thinned enamel by airbrush or spray gun, this must be done either after the first coat is not only dry but hardened, (which can take up to a week to reach this state), or it must be done within 10 minutes of applying the first coat. The reason for this is that the thinners in the second coat will often attack and wrinkle (known as pickling) the skin that has started to form on the first coat.

B) CELLULOSE
Cellulose primer will not attach itself to plastic or resin surfaces. Though it may have the appearance of applying well to the surface, what has been created is an egg shell over the model. Although you can apply any form of paint over a cellulose primer, there is a good chance it will crack and break away from the model in flakes right down to the bare plastic or resin, especially when removing any masking tape. If you must use a cellulose top coat then it can only be safely applied over an auto acrylic primer. Auto acrylics and enamels are quite safe to apply on top of a cellulose surface already in place.

C) AUTO ACRYLICS
This is not the same as water based acrylics, such as those made by Tamiya. The main supplier for good auto acrylic paint in the UK is Hycote. The Halfords own brand of auto acrylic is also made by Hycote. Grey primer is recommended for darker colours such as a dark green, blue or black. Lighter colours benefit from the use of white primer, especially red or yellow. White primer has the ability of keeping the top coats bright, whereas a grey primer used under a red topcoat will often affect the end colour result making it darker and more brown. Cellulose or enamels can be applied over auto acrylic quite safely. We advise not using red primer. We also advise that when painting metallics, they will require at least one coat of lacquer to bring out the best result of the paint.

D) TWIN PACKS and LAQUERS
A twin pack is a paint that requires a special thinner plus a measured amount of hardener to be added to the paint to make it cure. These are largely for professional auto use and require special breathing apparatus. We advise to avoid using twin packs unless you have no choice, (you can quite often recognise a twin pack paint as it smells strongly of pear drops). The use of lacquers to improve a gloss finish, is largely up to the individual. From personal experience, Humbrol clear gloss varnish No35 is about the best available for general modelling use. The satin varnish No135 is also good for side curtains on trucks and trailers where obviously a gloss finish is not required. These are both safe to apply over any paint finish and any brand of decals.

Other lacquers however, especially aerosols, may well negatively affect the surface of the paint, and can also ruin any applied decals, (which is because decal inks are treated with a clear varnish coat during production). Some decals use a cellulose varnish and some (all KFS decals) an enamel varnish. If in doubt use an enamel varnish such as Humbrol or a known waterbased product.

To view our other working with pages click on one of the below links

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