delamination describes the separation of layers, for example when separate layers made during the fibreglassing process fail to bond together.
demoulding is the common term for the unpacking of the prototype from the finished mould, also (though not as often) for the removal of the cast.
Depron is the brand name for a special type of styrene foam similar to the foam infill in standard foamboard but tougher, denser and supplied on its own without the paper coverings. It has a smooth but very slightly textured surface. It is manufactured principally as a thin insulation material i.e. under-floor, but because of its lightness and rigidity is very popular with model aircraft makers. Commonly 2, 3, 6 or 9mm thick. Special ‘foam friendly’ glues needed e.g. UHU Por (see ‘Styrofoam’) Obtainable depronfoam.com Price e.g. 3mm white 1000x700mm sheet £2.56, 6mm grey 1250×800 sheet £2.56 (2014). Not normally available in shops.
detail coat also referred to as the ‘impression coat’. The first thin layer applied, whether covering the prototype during mouldmaking or filling a mould during casting, to ensure that all surface details are properly filled. It is one of the most important factors in producing successful moulds or casts and worth taking trouble over.
dichloromethane (methylene chloride) often referred to by model-makers as ‘dichlo’ or DCM. A commonly used plastic solvent for melting/bonding certain plastics together (styrene, butyrate, ABS, acrylic, perspex). Architectural model-makers use this a great deal when building in white styrene because there are virtually no traces of gluing left outside the join. DCM is also recognised as a very effective general solvent and is a common component in paint-stripper. It is also one of the most dangerous to health! Model-makers commonly use a special solvent dispenser rather than taking from an open bottle, meant to reduce build-up in the air.
Safety data harmful to skin (can cause burning sensation, prolonged contact can dissolve fatty tissues), harmful by inhalation (particular hazard because when inhaled the body metabolizes it, producing carbon monoxide .. but apart from that can cause drowsiness, headache etc. Because DCM evaporates very quickly concentrations of vapour can easily occur especially in confined spaces. Classified as a Category 3 carcinogen in the European Community i.e. it has been linked to cancer.
Obtainable as ‘Plastic Weld’ solvent from E.M.A £3.45 per 57ml at 4D modelshop (2013)
DIGITAL IMAGING
I’m using this as a blanket term for the moment to cover methods of utilizing printed digital images directly in models, sculpture or other ‘real made things’. It could also include the use of the computer as a tool in the design development or creation process, but this becomes very broad! This entry is only in note form so far.
Keeping with the physical for the moment, photo printouts can be used quite effectively in ‘real’ 3D models to represent surfaces or even textures. See post ‘Using digital images on ‘realspace’ models – Part 1’ January 2013
www.cgtextures.com extensive, free visual database of natural and man-made surfaces including building facades, doorways and architectural decoration. Registration required, 15MB download limit per day. Choice of a range of resolutions/file sizes.
www.wallpaperdirect.co.uk good source of repeatable patterns. Right click on pattern image and click ‘Save background as.’
Recommended printing paper is WHSmith’s ‘Premium Coated Paper’ (a matte printing paper) price c. £6 for 50 sheets.
A good site for clear figure photos (useful for flat model figures) is www.kaboodle.com
dimensional paint sometimes used to describe thick, liquid media used for decorative relief work, which can be painted or ‘piped’ on and will keep much of their volume when dry. See ‘relief paint’
directional difference sheet plastics such as foamed Pvc are machine-extruded and can exhibit slightly different properties in the direction of extrusion, sometimes referred to as the ‘machine direction’ and usually the length of the sheet compared to the width or ‘transverse’ direction
double-sided tape is a thin plastic film in tape form which is coated with adhesive on both sides, supplied with a protective covering which needs to be peeled off after applying to a surface. Available in a number of forms and strengths ranging from low-tack for draughting purposes to high-strength carpet tape. £shop tape tends to be weak but fine for temporary work. ‘3M’ brand tape is more reliable. Atlantis shop version (25mm wide £4.55, 2013). Carpet tape type e.g. ‘Rhino’ from Ultratape very reliable (c. £1.50), Wickes double-sided flooring tape 50mmx25m £3.50 (2013)
dovetail a term, and a method, borrowed from carpentry describing the shape of interlocking parts, in this case cutting ‘dovetail’ (triangular) shapes into a silicone mould edge so that it will interlock with the supporting jacket.
dry brushing is a painting technique where, starting with a dark ground, a minimal amount of lighter colour is evenly distributed on the brush which is then lightly skimmed or ‘dusted’ onto the surface. This will pick out surface details in a similar way to ‘brass rubbings’ and works best for emphasizing textures.
eggshell crushed in a mortar, useful for model leaf coverage. Best painted with watercolours
elevations in technical drawing are full views of the vertical faces of the object or structure being drawn
embossing usually implies pressing a hard, smooth tool into a relatively soft surface to create a permanent impression without breaking the surface. A decorative technique. Special ’embossing tools’ can often be found in hobby shops and usually consist of a steel point which is rounded into a tiny ball at the end
ENAMEL PAINT
As a general paint term, ‘enamel’ paint is distinguished by being very hard-drying and durable, a suitable paint for objects subject to wear i.e. furniture, toys etc. It is sometimes referred to as ‘cold enamel’ to distinguish it from the very different technique of fired enamel work.
For many it may be familiar as the small (14ml) tins from Humbrol or Revell. A thin but opaque, quick-drying oil-based paint designed for plastic or metal (will even stick to latex). Available in gloss, satin or matt. Matt versions dry very matt, more so than acrylic. Can be thinned with white spirit to make washes or stains. Will keep indefinitely if tin is properly closed (rim should be kept clean). Must be thoroughly stirred before use. Obtainable model/hobby shops, some art shops Price £1.30-1.80 per tin (2014)
Advantages sticks to anything; high opacity and an even, non-streak coverage; does not cause warping of card or paper; can be used directly as primer; matt version dries properly matt; quick initial drying ( matt version 20-40mins) and over-painting possible, full hardening 24hrs; dries to a thin layer, does not clog fine detail; although tins are small the paint can go a long way because it can be spread very thinly.
Disadvantages limited colour range (few vibrant colours) more ‘earth’ colours; needs to be thoroughly stirred before use because ingredients sink; strong solvent emissions and requiring white spirit as thinner and for cleanup, ventilation essential; because it dries quickly it is not a paint for ‘wet painting’ i.e. being able to move it around and blend, as one can with artists’ oil paint.
Best sources for online ordering June2013 www.wonderlandmodels.com specializing in Revell enamels but also stock Humbrol. Currently Revell 14ml tins £1.28, Humbrol 14ml tins £1.36 (these prices include VAT). Standard delivery (under £70 worth) is £3.00, express delivery is £6.00. Delivery was very fast (within two days) even with Standard
exothermic describing a chemical reaction that generates heat, for example when the two parts of resins such as polyurethane or polyester are mixed
fence describing the thin wall (usually pieces of thin metal sheet) inserted into the surface of a soft clay sculpture in order to divide the form up into separate areas for mouldmaking
fibreglass specifically refers to thin filaments of glass which are woven or pressed together to make a flexible matting. When ‘laminated’ (layered) in combination with polyester resin a very strong but lightweight shell can be formed. The combination is often referred to as GRP meaning ‘glass reinforced plastic’. Because of harmful emissions, fibreglass work should never be carried out indoors without an extractor fan and/or proper respirator masks!
Most of the following information relates to creating a hollow fibreglass cast in a silicone mould, as detailed in the posts ‘Making a hollow 2-piece cast in fibreglass’ August 2012
Method of fibreglass lamination The first task is to catalyse some straight resin and lay down a ‘detail coat’ i.e. ensuring that the mould is covered with a thin layer (which will become the surface of the cast) before matting is used. This can be pigmented, filled, or even gel coat used, but taking care not to make too thick i.e. average 1-2mm. When this is firm, still tacky perhaps (c.15-20mins), more resin is applied to wet the surface and small pieces of matting ‘pasted’ down, soaking with more resin in the process until gradually the area is covered.
As a note here, it is important to follow the ‘detail coat’ with the first matting-filled layer as soon as possible after the detail coat has firmed up. Unfilled polyester resin will shrink, so for example if the detail coat is left curing in the mould for more than a day it may start to pull away from the mould surface or (if the silicone is a thin skin) take it with it, distorting the cast. As a rule the presence of fibreglass matting in the subsequent layers counteracts this shrinkage if it is ‘arrested’ soon enough.
Matting layers are repeated a number of times according to the thickness and strength of the fibreglass needed. I usually mix up just 25g of resin each time and patch pieces of matting c. 10cm sq (because with this amount and my rate of working I generally use up all of the resin just as it’s beginning to turn to a gel). Obviously the speed with which one can work depends a lot on the topography of the form being covered. I use cheap 1/2inch or 1inch painting brushes, cleaning them quickly in acetone for re-use straight away. The most common matting for medium-sized work is ‘chopped strand mat’ at 300gsm weight, av. £1.50-£3.00 per metre (specialplasters.co.uk, Tiranti). There are heavier versions, some woven instead of just compressed but these are more suitable for large-scale work such as boat building. Glass fibre is also available in ribbon form (for edging), as loose chopped strands or in a thinner tissue form.
When mixing up small amounts of resin like this it is common practice to add more than the usual proportion of catalyst to ensure curing. The usual for large amounts (i.e. 200g upwards) is 1% catalyst, but I usually add 2% or even 3% when mixing small amounts such as 25g
Tiranti’s guide to layers (using 300gsm mat) up to 8ft 4 layers, 8-12ft 5 layers, 12-16ft 6 layers, 16-20ft 8 layers.
Reliable further information on working with fibreglass, or with resins generally, can be found on the CFS site as ‘how to’ guides or material summaries i.e: http://www.cfsnet.co.uk/acatalog/methods_applyinglaminate.html
Rough notes
Conditions ideal temp 15-20, no damp and good ventilation. Avoid direct sunlight on moulds. Protection i.e. latex gloves, but these can easily get too sticky! Extras inc. disposable brushes, and/or acetone First coat i.e. ‘detail coat’. Can put in up to 3% catalyst, 2% will give 15-20mins pot life. Must harden to ‘tacky but firm’ (1-2hrs room temp) before adding second layer with matting (apply second layer within 24hrs). Resin needed very rough ‘rule of thumb’ 1kg of mat needs 2.5 x resin. Wet out first layer first and paste matting, wetting out more with a stippling action. Not necessary to wait for setting between these layers (though waiting can help reduce heat generated if applying more than 3 layers)
‘flow-coat’ gel coat with a wax additive.
AL head 2012 (see posts August 2012) Mainly used Tiranti MP (‘Multi-purpose’), mainly just 2 layers of 300g mat. 1st layer 10% white pigment (worked in 25ml batches with c. 14drops cat). 2nd layer 6tsp Fillite per 25ml resin
Suppliers
Tiranti www.tiranti.co.uk
CFS Fibreglass www.cfsnet.co.uk
East Coast Fibreglass www.ecfibreglasssupplies.co.uk Prices (inc.cat) but before VAT/- 1litre,5litre ‘White’ Lloyd £7.50, £19.95. Standard Lloyd £5.95, £17.95. GP £5.50, £16.50. delivery £9.50 up to 20kg (2012)
Disposable brushes for fibreglass work
Brushes don’t necessarily have to be used just once and then thrown away, they can be cleaned of polyester resin (before it has cured) by swilling in acetone. But it’s better to use cheap brushes because it does affect them.
99p Store Black Dog brand 10-piece brush set (1.5-0.5inch coarse natural hair brushes). Other packs of synthetic bristle painting brushes (2.5-0.5inch) from Poundland. Acetone will not dissolve them though it will start dissolving the lacquer coating on the stocks
fibreglass tissue is a very fine, thin form of fibreglass matting which becomes much more mouldable than the heavier, regular forms of matting especially when it is wetted with resin. It’s most suitable for laminating over detailed or sharply undulating surfaces especially where less structural strength is required.
There are alternative, certainly cheaper, materials to use in place of fibreglass tissue though perhaps not as strong i.e ‘Bamboo Fibre Cloths’ from ‘99p Store’ pack of 5 38x50cm.
FILLERS
Fillers are commonplace in a wide variety of everyday materials .. paint, cosmetics, even the food we eat. Arguably the main purpose of a filler is a commercial one .. to bulk-out a substance with an inexpensive material so that the manufacturer can sell more of it for the same production costs. But fillers may also be necessary to make the product work .. or taste .. better. Here, in the context of materials for making and particularly for mouldmaking and casting, fillers economise, or change the weight, enhance the appearance or alter the working properties of many of them. One fundamental of a filler .. whether added to a paint, silicone, plaster or resin .. is that it doesn’t affect the chemical behaviour, and thus the curing or hardening. A filler usually has to be ‘inert’.
For a complete account of various fillers see ‘Common fillers for resin casting’ under ‘casting’ in the ‘Materials’ section. Here is a selection:
Fillite an industrially manufactured ash material, light grey in colour, used for filling resins etc. Fillite is inert, meaning that it has no chemical affect on the substance. Fillite particles are smooth and rounded, like microspheres, meaning that small amounts will not affect the flow of a liquid. Fillite is also very light. Price £4.56 per 1kg, £14.10 per 5kg (tomps.com 2013) Resin will generally accept up to 4x its volume of Fillite without affecting setting process but this will produce a paste. Generally the mixture starts to become too thick to pour easily after 1x volume of Fillite. Note 2014 the price of Fillite has gone up considerably in recent years, and suppliers are finding it no longer so economic. Check current suppliers and prices in ‘Quick view comparisons of casting materials’ in the ‘Materials’ section.
Tea/coffee grounds with PU resin. Using these will impart a woody or warm stone look to the resin dependent on how much is added. Tea will also make the cured resin much easier to carve, similar to pumice. Adding a lot of tea (i.e. 30% upwards) can cause the resin to foam and the mix to expand a bit .. though this may be due to moisture remaining in the tea powder even though this was left to dry for a number of weeks. In the case of tea particularly, the particles will expand immediately when added to the resin so it is unlikely that the mixture will be pourable .. more pastable! It is important (in the case of all absorbent materials utilized as fillers) that parts A and B of the resin are properly mixed first before mixing in the powder. See post ‘Filling polyurethane resin with used tea or coffee’ from May 2013, especially for info on proportions used.
Tests May 2013 tea and resin (both parts together) in equal weight gives a soil-like solid but still pastable into a simple mould; 2:1 weight resin to tea gives a more moist soil; 3:1 weight resin to tea a wetter sludge, giving a smoother shell coating. 2.5:1.5 weight resin to coffee for smooth, rich brown surface.
Fine sawdust is also suitable as a filler, but fine-grade sawdust is not that cheap. Fine pine sawdust from e.g. www.oldpinecompany.co.uk costs £5.00 per 1kg bag (£5.00 delivery)! Fine wood dust of different types also obtainable from home food-smoking suppliers av. £3.00 per 250g. If used with resin, like tea they will absorb and expand quickly. Obviously there must be far cheaper sources of fine sawdust .. I don’t know of them yet .. and yes, much coarser sawdust is readily available from pet shops, or as scenic material from model shops.
Fillite see ‘Fillers’ above
filter granules Brita filters contain a mix of granules of ‘activated charcoal’ (usually burnt coconut shell made more porous) and minute beads of ‘ion exchange resin’. The activated charcoal (carbon) removes odour and removes the taste of chlorine, and the resin beads lower concentrations of calcium carbonates, softening the water. The reason why I’ve included it here is that the granule mix looks interesting and ideal, when painted, as a ‘scatter’ material to simulate leaf cover on model trees. It could also make an interesting filler for resins.
finger paints or ‘rub on’ paints e.g. ‘Finger Gold’ see ‘wax gilt’
Finnboard (from Finland) is an attractive beige/cream-coloured cardboard with a slightly rough surface, a little cheaper than mountboard, lighter, softer and less liable to warp. Unusual in that it’s made totally from wood pulp. Can be soaked in water and then bent into curves, rather like dense felt. Available 0.9, 1.5, 2, 2.5 and 3mm thicknesses. Because of its sympathetic colour, price and ease in cutting it’s an ideal sketch-modelling material. It is not lightfast, therefore it will darken noticeably in sunlight Obtainable see ‘Quick view materials info’ under ‘constructing‘ in the ‘Materials’ section for current prices and suppliers. So far I have only seen this available at 4D in London or Modulor in Berlin
flashing or flash is a special term more common in industrial casting to describe the thin ridge that forms when casting material leaks along the seam line during casting and hardens there. This can usually be easily removed and the seam cleaned up.
florist’s wire Traditionally, short (c. 30cm) lengths of very soft, often dark, bendable wire useful for bunching/bending for tree armatures etc. Obtainable craft shops, some old-established ironmongers .. perhaps even florists!
FOAMBOARD
The standard type is most commonly a layer of polystyrene foam between two layers of thin card. Available 3, 5 and 10mm thicknesses (though both 3mm and 10mm often more difficult to find). Black is also common but only in 5mm, and paper can often be peeled fairly easily from the black type. The surface of standard foamboard tends to be fragile (dents easily) and the foam, because it is polystyrene, is attacked by solvent glues and spraypaints. Price c.£5-6 for A1 sheet.
Think carefully before choosing standard foamboard for anything but sketch or ‘white card’ model-making. It may be convenient for plain walls but certainly not for detailing. Will warp badly, difficult to cut precisely, edges and surface will be fragile, difficult to glue.
See also ‘Kapa-line Foamboard’ for the superior, denser, polyurethane foam type which can also be used as a shaping/texturing material.
foamed Pvc (see ‘Palight’) a sheet form of Pvc which is foamed inside to make it lighter, developed for signage and display purposes. Both surfaces are smooth but the porous interior makes it very easy to cut, even with a scalpel, and also helps it to maintain its straightness. White is most common, but colours are also available in some thicknesses and it is normally supplied as 8x4ft (2440x1220mm) sheets
GELATINE
Gelatine (or ‘gelatin’) is a translucent solid derived from the collagen obtained from animal by-products. It can commonly be bought as granules in any supermarket and is used in cooking for thickening and for making ‘jelly’.
A special recipe for a mouldmaking compound involves a concentrated mix of gelatine granules dissolved in water, with glycerine and thin honey added. Heated in microwave, set in fridge. Reusable. Melts at 49C.
Directions 4 sachets of ‘Super Cook’ gelatine crystals (75ml) in cup. Fill 2nd cup with half amount (37.5ml) warm water and top up to 75ml with runny honey (Tesco value). Stir to dissolve and pour into container. Add 75ml glycerine to container. Warm container in microwave full power c.20secs and then stir well (should be warm-to-hot). Add gelatine and start stirring in (heating and stirring until gelatine is dissolved). Let cool and put in freezer/fridge for a few hours. Gelatine needs to be warmed carefully in a ‘bain marie’ (or similar improvised setup) to make liquid again to be poured over prototype to make a mould.
7/2013 since gelatine presumably has to retain its water it may not be a suitable mould material for resin casting, but see ‘Casting polyurethane resin into alginate’ November 9th 2012.
‘Composimold’ similar US product. Melts at 49C
gel coat refers either to the first coat laid down when laminating with fibreglass (often slightly thickened) or to a specially bought, pre-thickened resin preparation for the purpose
Gelflex see ‘Vinamold’
gesso is a chalky undercoat for priming bare canvas or board as preparation for painting. Nowadays ‘acrylic gesso’ is more commonly available, though this will have different properties from the traditional form of gesso which was made from chalk and animal size.
glass-etch spray a special aerosol spray coating which matts the surface of glass or other clear surfaces for a ‘frosted’ look.
gluing from outside Not a common term but the only one I can think of for describing the technique of using a water-thin glue (either thin superglue, or dichloromethane when working with styrene plastics) applied along a joint after pieces are positioned. The glue is sucked into the joint by capillary action and usually bonds the pieces quickly and firmly as long as they’re flush together. Sometimes it’s the only effective way to glue certain things together, for example if elements need to be in an exact place and repositioning is not possible
gouache is an opaque, matt, water-based paint normally only used on paper .. really just an opaque version of watercolour. It contains a high proportion of filler for opacity, minimal binder (gum Arabic) and often glycerine to help it ‘flow’ better. Lighter colours dry darker, dark lighter! The filler means that it covers evenly, usually without streaking. Because it contains minimal binder it will not normally stay well on non-absorbent surfaces such as Pvc or Sculpey, but can be modified by mixing in an equal quantity of Pva wood glue (e.g. Evo Stik Wood). In my experience this will not normally make the paint dry silky though it can if too much Pva is added.
green stage refers to the soft state of a resin cast when it is just firm enough to be taken out of the mould but may still be pliable (in the case of polyurethane) or has not yet reached it’s maximum hardness and can be more easily trimmed. Usually at this stage the ‘flashing’, i.e. any resin which has travelled into the mould seam, will be much softer than the main body making trimming even easier. This is because thin sections of resin cannot get as hot during curing as the main body therefore curing is more gradual.
grout which is used for filling the gaps between ceramic tiles can be used as a casting material, as it is normally just a type of cement. It is supplied as a powder, to be mixed with water. e.g. Mapei Ultracolor Plus £15.99 per 5kg (ScrewFix 2014) available in different colours. Hard, smooth finish, long-setting c. 3hrs
GRP see ‘fibreglass’
heat gun a special tool available from building/DIY stores, normally meant to assist paint stripping. The DIY versions look like oversize hair dryers and deliver a heated air stream ranging between 50-600C. Smaller, more manageable versions can be found in craft/hobby shops e.g. ‘heat tool’ £12.99 (2013) from Hobbycraft. There’s a very good and inexpensive one from Wagner, the HT400, which was selling at B&Q for a brief while. Now they’re nowhere to be found in the UK but in the US they can be found at Walmart. Heat guns are very useful for hardening polymer clays (rather than using an oven).
hogshair brush usually used for oil painting where the stiff bristles help in spreading the paint evenly
homogeneity in the case of modelling materials homogenous means ‘the same consistency and behaviour throughout’ i.e. without hard/soft variations or lumps
Idenden Brushcoat is a specialist water-based texturing paste popular with scenic workshops in the UK. It is made by a division of Bostik, for thermal insulation and fire protection. It dries durable, flexible and without too much shrinking. It is designed to adhere even to polystyrene or vacuum formed plastics and is also flame-resistant (Class 1, BS476 part 7). Available in opaque white, grey and black and will accept pigments for colouring. On the negative side .. it is expensive because only available in 10 litre tubs! Price £83.94 per 10litre from Flints www.flints.co.uk See also ‘relief paint’
Imperial the system of measurement using feet and inches
impression mesh Many different types down to extremely fine. Defined by diamond-shaped openings, punched out of continuous sheet making it mouldable (the diamond shape can expand or contract easily) . Usually copper or aluminium. Obtainable 4D modelshop; B&Q (some stores have heavier versions) Price varies (expensive in craft/hobby shops)
inert in the case of filler materials added to resin, meaning not chemically active, so they will not affect curing
intermediate casting is done, for example, when a prototype form or roughly modelled figure is first made, a mould taken of it, then cast in another material which is easier to refine before making the final mould. This is a common practice in commercial toy design where a harder wax copy replaces the first sculpt and this can then be more perfectly smoothed or machined for an ‘industrial’ finish. It also constitutes an important part of the traditional ‘lost wax’ casting process where the initial clay sculpt is copied in wax which is then replaced by metal during casting. Although time-consuming, it can also be used as a way of ‘saving’ stages of the modelling process.
investment casting see ‘lost wax’
ISO 216 (International Standard) sizes A4 210x297mm, A3 297x420mm, A2 420x594mm, A1 594x841mm. Unique aspect ratio (the proportion of length to height), the same if sheet is divided in half.
isopropyl alcohol also known as ‘isopropanol’. Colourless liquid, evaporates quickly. Miscible in water and alcohol. One of the least toxic of solvents or cleaners, but good ventilation is as always still necessary. Sometimes referred to as ‘rubbing alcohol’ but see ‘Surgical spirit’ below.
Uses as a cleaning agent in precision engineering, optics and electronics; solvent for natural resins and gums including shellac; dissolves oils; removes some sticky label glues; preserves biological specimens
Safety data highly flammable; toxic if swallowed or inhaled; irritating to skin; vapours can cause drowsiness or dizziness
Obtainable for current prices and suppliers refer to ‘Solvents and thinners’ in the ‘Materials’ section.
davidneat 