Diecast vs Resin: AUTOArt and Spark Debate the Issue

In the world of diecast models, there’s often quite a debate about whether diecast or resin is the best option for creating beautifully detailed replicas. Normally you would associate this debate with a heated discussion down the pub after a swapmeet or a conversation between collectors of the respective types. However, now the actual manufacturers have stepped into the ring with AUTOArt saying that diecast is more “challenging” to work with but resin is much faster, while Spark has come out and rather bluntly stated: “there is a lot of nonsense spoken and written about diecast metal or resin as the best material for collector’s models”.

It seems in particular that Spark has taken offence to an article AUTOArt published on its website in September explaining why the manufacturer doesn’t produce resin models. The piece goes into great detail about the negatives and positives of both materials, explaining that the cost of diecast moulds is very expensive. Here, we’ll produce both sides of the argument to help you make your own decision about which is best.

RESIN IS JUST FOR SMALL NUMBERS

“Tooling a full set of die-cast steel molds for one model is expensive. The tooling investment for a 1/18-scale model car can be in the region of US$100,000 to $200,000, depending on the complexity of the model and the number of components,” explains AUTOArt.

  Spark Lotus 76, No.2, Austrian GP 1974 Jacky Ickx

Compared to a silicon-rubber mould the costs and time are astronomic, a resin mould only costs a few hundred and can take just a few days to complete. As such, AUTOArt concludes “resin is thus the ideal material for manufacturing a small quantity of model cars, in any scale, especially ones that require the shortest possible lead time for launch into the market”.

However, although Spark agrees that resin does allow for shorter manufacturing times, it doesn’t believe AUTOArt has painted the full picture about the costs involved. “When Auto Art refer to the comparative costs of tooling and the considerably greater cost of steel versus silicone they are only telling part of the story. A major cost component of any particular model comes from the research necessary to ensure accuracy. We employ a team of specialists with different fields of expertise, whether it be in classic F1, Can Am, Land Speed Record or whatever.”

DIECAST MODELS ARE STRONGER

Although AUTOArt states that it’s faster and easier to produce resin moulds, it goes on to say that there are large negatives to the material. “There are major shortcomings to resin models, mainly in the nature of the resin material itself. It is much weaker structurally than die-cast zinc-metal, and it may deform after some years as it ages. Working doors and bonnets cannot be made accurately, with a fine air gap around them, because a doorframe cast in resin is not rigid enough, especially in the area of A- and B-pillars.

“Moreover, the fixing of the hinges is also very fragile, and they can easily break if not handled carefully.  Therefore, to avoid such problems, most resin models are made without any working doors or bonnets.”

Again, Spark has a different view on this subject. “Auto Art is certainly right to point out that it is generally easier to produce opening doors etc in diecast as resin is fragile. However the problem does not completely go away in diecast as one is still often left with the choice of overscaling the hinges and catches or else making them so delicate they also break easily. Collectors still have to make up their own minds on whether they want opening parts or not . These can be very successful on some cars but not necessarily on all.”

But it is the idea of ‘deformation’ that Spark takes particular offence at. “We have seen none of the structural deformation in resin models that Auto Art suggest is possible despite the fact that we have some that are forty years old in our personal collections. Their comment strikes us as being biased scare mongering.

“It also neglects to mention that there have been well documented cases of diecast zinc deterioration commonly known to collectors as "metal fatigue" which can result in blistering, expansion, distortion, cracking and even total collapse of zinc castings. It is only fair to say that this should not occur in well controlled production processes and indeed I have many sixty year old Dinky Toys and Solidos which are as perfect now as the day they left the factory.”

PAINT PROBLEMS FOR RESIN

AUTOArt continues its criticism of resin by saying that the paint finish on diecast models is often superior. “When it comes to painting the model, there is also a big difference between resin and zinc. Paint requires baking time in an oven to cure properly, a step needed to ensure the paint achieves an accurate glossiness. Such oven curing can be done on metal, but not on resin, which will deform in the heat of an oven.

 “Thus, the paint used on a resin model cannot be oven baked; it requires extra clear coating to achieve the desired glossiness.  So while the color painted on metal will yield a similar effect to a real car, the paint finish on a resin model can appear very glossy, but only with clear coating, which somehow lacks the look and solid feel of single-step painting.”

Spark goes on to call this claim nonsense! “We take issue with Auto art's comments regarding the baking of paints. We do bake paints in our factory on both resin and diecast models - so they are simply talking nonsense here. The glossy appearance that they mention is not inherent to the process of painting on resin but a commercial /aesthetic choice that some manufacturers have made in response to their clients' demand for a glossy finish. As it happens we do not like the glossy finish as we feel it makes the cars look as though they are covered in treacle or honey.”

DIECAST DECAL DILEMMA

Finally, another point the two manufactuers dispute is how to print the liveries on models, with AutoART preferring pad printing over water decals. “On resin models, colorful racing liveries are mostly done with water decals due to the small quantity of models being manufactured.  Pad printing or ‘tampon’ printing yields a better result than using water decals, because the colors are printed directly onto the body rather than printed onto the decal membrane.

“But the pad printing process involves high setup costs, especially if the livery consists of many colors, and that’s only economically feasible if thousands of pieces will be manufactured. Therefore, practically all the racing versions of resin models use water decals.   Water decals age and can become brittle and vulnerable to scratches after some years.  They also require great skill to apply precisely, and on the assembly line, maintaining a consistency of workmanship among the models becomes problematic.”

Guess what? Spark doesn’t agree with this statement either. “We also take issue with what we would regard as oversimplification of the choice of pad printing or decals. We use both methods and the choice for us depends on the individual application. Pad printing can be unsuitable for surfaces with any great degree of compound curves. They are typically appropriate for the flatter surfaces of a car far, less so on any distinct compound curve.

“So any given model of ours, whether it be diecast or resin, will have a mixture of pad printing and decals.  The issue of the transparent membrane yellowing with age becomes obvious on a white or silver background but is not noticeable on most other colours, even on my old 1960s Solido models.”

IN CONCLUSION

In its final statement AUTOArt makes it very clear about the future of the models it produces. “Other than special project, AUTOArt will not go into the production of resin models or make it part of our mainstream product program. We believe die-cast metal, along with injection-molded plastic, is the most ideal material to make an accurate and collectible model car to our standards of excellence.

AUTOArt Alfa Romeo 155 V6 TI DTM 1993

Die-cast metal is harder and more challenging and costly to work with, but the model can be made with much finer detail overall and at a more affordable price.  It is structurally more rigid, and it will bring pleasure to its owner for much longer.”

Meanwhile, Spark doesn’t mind which it uses because it believes both are suitable. “Lastly we would really like to emphasize again we don't care whether a model is made of resin or diecast zinc. We only care if it is accurate or not. Any good scale model, diecast or resin, is a fragile and delicate object. It is not a toy to be pushed around on the floor.”

So, what do you think? Let us know in the comments below… and please don’t argue like Spark and AUTOArt.