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  • Dull scum floating atop of melted pewter - silicone rubber low-melt metal
    This is simply the impurities in the metal coming out. To discard, skim off with a spoon. This is really important, as the scum impurity will weaken a casting.
  • Creating a 'marble' look in casting
    To do this, firstly, partially blend liquid colouring into the resin mix (no more than a couple of swirls). Next, pour out the mix in a swirling motion as the mould begins to fill up.
  • Release agents for concrete casting into polyurethane flexible moulds
    Your best bet is kerosene and oil mix. The rule of thumb is: one part oil to three parts kerosene.
  • Casting comprising 'sticky' areas
    Generally speaking, this is typically a sign of poor mixing. Unless both parts A and B are thoroughly mixed together, any undermixed material will not cross-link fully and, in turn, remain sticky. Mix thouroughly in a straight-sided, flat-bottomed container (using a flat ruler-shaped mixing stick), scraping around the sides and base of the container.
  • Pigments and dyes shelf-life
    Generally speaking, you can store these for many years. If separation does occur, however, simply re-mix, or, if the material has dried out, add a small amount of metholated spirits.
  • Creating a shiny finish on pewter casts
    Your best bet is to use a jewellers polishing compound, bearing in mind that a glossy mould surface will make the metal brighter. Just make sure that the original pattern is glossy before casting the low melt-metal silicone rubber.
  • Flow issues with pewter into a closed mould
    Very simply, when pouring a hot met into a cold mould, the mould, itself, cools the metal quickly and, in turn, stops the flow, resulting in 'partial casting'. The best rule of thumb is to preheat the mould in an oven. This, combined with dusting the mould surface with talcum powder, will assist slip and flow in the pouring process.
  • Working out how much casting material you'll need
    Here, the best rule of thumb is to fill the area (that you're going to fill) with, say, water, sand or rice (or something similar). Then, pour this amount into a measuring container. The resulting level on the measuring container will give you the amount of liquid you will need. In turn, add an extra 10% to this amount, as this will take into account any losses that occur during during the pouring process. To convert a volume to weight multiply by 1.2 as most resins, silicone rubbers and polyurethane weight around 1.2kg per liter.
  • Casting an object suspended in clear epoxy resin
    Firstly, cast up to the level where the object is going to set, and letting the resin partially set, bearing in mind that cast epoxy resin will generally firm up within a couple of hours (you can monitor this by checking the resin and applying pressure with a needle, which is better than using your finger, as the latter will leave a fingerprint). The best rule of thumb is to cast subsequent layers of resin after the previous pour has had time to set up and come down in time from its peak exotherm point (layers should be cast within 24 hours of each other. This is to help eliminate visible joint lines between each layer of resin). Once firmed up, place the object to be embedded on top of the resin, before pouring a new resin mix to top up the mould. in turn, this technique can be used to cast multiple layers - clear or coloured - with an embedded object.
  • Why does the colour of an organic specimen change when embedded?
    This can be caused simply by the resin heating up during the caring process. To ensure this doesn't happen, restrict the volume of resin, or try casting in several layers.
  • Preventing paper or photographic images from darkening or discolouring when coating with resin
    The best bet is to, firstly, apply a thin coating of PVA adhesive, or a spray photographic fixative. From there, let it dry. Then, coat or embed the paper in resin.
  • Bubbles forming when embedding an object
    It's possible that air could have been present in the object you've embedded. In turn, warmth generated when the resin is setting causes the entrapped air to expand and, subsequently, create bubbles in the resin. A dried insect, for example, can still hold air in its body. Here, once the resin has been exothermic, the air will draw out. your best bet is to pre-seal the object with a thin coating of resin first. From there, let it fully dry, then embed the object.
  • Embedding organic objects in epoxy resin
    Generally speaking, you need to allow adequate time to dry an organic object, just to ensure it's thoroughly dry and devoid of moisture. In turn, not doing this will mean that it could decay and rot within the resin once the exothermic reaction takes place. The other consideration to take into account is that moisture will inhibit the resin cure.
  • Pattern shapes that aren't suitable for moulding
    The key thing is undercuts. The object shouldn't be so complex that your mould halves (or multiple sections) can't be withdrawn without excessive undercuts - a 'tree', for example, is to delicate to be able to practically cast.
  • Eliminating bubbles when pouring out silicone or casting materials
    Generally speaking a vacuum pump is your best bet. Beyond this, there are several steps you can take to reduce the likelihood of bubbles. Firstly, mix materials in a steady figure-8 manner, ensuring that you mix the material on the mixing container sides. In turn, avoid lifting the material on the mixing container sides (and avoid lifting the mixing stick up and down). Then, pour the mixture out by pouring close to the work (and from one point). Slowly lift the mixing vessel to about 40cm above the work, and be sure to pour in a very thin stream (this will ensure that any air bubbles present are torn open as the material pours). In particular, avoid lacing the material over the work as this captures air. Keep pouring from one point, letting the mixture flow out evenly over the work like a slow wave.
  • Why does a part become difficult to remove from a mould
    This typically indicates that the mould has reached the end of its life, so to speak, particularly where small pieces are starting to tear away. In turn, the casting life of a particular mould varies depending on the number of casts that have been made from it, the type of casting material, as well as the overall complexity of the object and, in turn, the mould, itself.
  • The curing of epoxy resins
    Epoxies, in particular, are very temperature sensitive. A temperature drop to 15°C (or lower) overnight will kill off cross-linking of the mixture. In turn, resins need to be consistently kept at 20°C (or more) for the entire cure period. Uncured epoxy resins may respond to later application of extra heat, but some may never revive and, in turn, will remain sticky. If this happens, you can wash off with warm, soapy water, dust it with talc or apply more resin mix to bond the sticky surface.
  • Protecting copying electronic components set within clear resin
      to do this, colour the casting material with an opaque pigment.
  • Achieving a metal-finish look when casting
      Beyond this particular look, the following method applies for any cold-cast material. In turn, optimum results are achieved by using a leafing-grade metal powder (in other words: a metal powder that transfers a full metal powder coating onto an item dipped into the powder). Very simply, use a dry brush to paint the mould surface in metal powder. Then, mix the powder into the casting material to achieve the same colour. From there, pour the casting material in. Upon removing the casting, buff the surface with a soft cloth. the overall look will be a low-sheen metal effect.
  • Creating a rusty look
    To do this, dust the mould with iron powder. From there, colour the casting mix to a rusty brown colour with acrylic paint pigment. Then, pour in the casting material. Upon removing the casting, dust down, then spray diluted hydrochloric acid onto the gray iron powder surface. Lastly, let sit for 24 hours. The resulting casting will have a rusty-iron look (all over) - combining a mixture of actual rust and rusty-coloured material in some background areas.
  • Where an object is too large to post cure in an oven
    When you are using, say, Solid Cast 606 epoxy resin, which typically requires a post cure of four to six hours in an oven, larger objects can simply be placed under a table or some larger framework, draping over with a plastic tarp or blanket.
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