The debate still rages on with regards to the best sulphur free clay on the market today. What we have to realize is that every manufacturer of this type of material will be continually developing their product to prevent any loss of business, afterall, most auto manufacturers use this material to develop their future products. Modelers of all nationalities have their own opinions on what material should be used especially with sulphur free but the unfortunate reality is in most circumstances, the company policy where they work dictates the material to be used.

I’ve been in the position to have used or witnessed the offering in sulphur free clay from three of the main players, Chavant, Eberhard Faber and Kolb. To give you a more detailed description of how these clays face-off against each other, here is a more in depth review.

Chavant V130

• Compared to earlier versions by Chavant this finishes very well, allowing for spot check highlighting without the use of film by experienced modelers. Lesser experienced modelers will still have to view the traditional way, with dinoc or highlighting film.
• Once applied, the clay firms up very quickly which is good for instant modeling but can be a disadvantage, especially when priming bucks with a substantial amount of clay. A heat source would be advisable to ensure all clay layers adhere to each other to prevent delamination.
• Does not blend very well without an external heat source.
• Still has adhesion problems although better than previous versions.
• Substantially less abrasive than previous versions but still requires frequent sharpening of tools. The main culprit from the previous version was the glass spheres that were used for the filler, once the clay was brought up to temperature it blended very well but any length of time in the oven, i.e. 2-3 days would see a glazing of the billet surface. This glazed surface would not blend into the rest of the billet, giving an appearance of small pieces of shale in the mix, resulting in the steels skidding off the surface rather than cutting.
• Color still remains patchy due to aging in the oven and oven temperature change. Regardless of how consistent the oven temperature is the color will darken with age due to the materials used.
• Detailed edges are hard to repair or change. (Adhesion problems)
• Edges tear in any profile dragging process unless clay is keep very warm. This amounts to addressing small drag sections at a time as the clay cools very quickly. I would recommend an additional heat source such as a heat gun to rewarm surfaces prior to putting in any profile.
• Still susceptible to cracking. This you can probably put down to a 50/50 problem, 50% being the buck building process and 50% down to the lack of elasticity in the clay. The buck has to be tight, that is, no voids in foam joints and I mean, no gaps whatsoever otherwise the clay will eventually crack in that area. The clay has to be packed on correctly, in even layers and not by building up walls and filling in between.
• Machines very well although feed has to be slowed down to prevent cutter bounce.
• Machine finish is not as good as the sulphur based clays.
• Machine cutters require a regular re-sharpening but the abrasion issues are not as visible as in previous versions of sulphur free.
• This latest version of sulphur free still remains a hard clay to work with which will affect productivity in model changes. I would estimate a 25% increase in time in manual labor on any model change.
• There is a certain amount of delamination of the clay in areas that have design tapes affixed, again proving there is still an adhesion issue.
• Painting the clay proved to be a none issue. Using the recommended claypeel as a barrier no adverse effect was noticed.

Faber Clay Light (3rd Generation)

• Very soft compared to the Chavant ( Softer than I307 and Y2klay V130)
• Color is a light brown/mocha, needing dinoc film or highlighting film to spot check highlights. I would prefer a darker color.
• Surfaces very good with far less effort and abrasion to tools.
• As the clay is softer it is far more modeler and design friendly, good for quick changes.
• Lower heating temperature than Chavant.
• Compared to Chavant it has good adhesion properties although it still displays some delamination from tapes.
• Faber is certainly more on the oily side making it harder to apply tapes. Tapes tend to creep after a certain amount of time on the model surface, more than the clay by Chavant.
• More elasticity than Chavant with no visible cracking but to be fair a scale model cannot compare to a fullsize model.
• Machines very well with no cutter bounce.
• Like Chavant, requires an outside heat source to fully blend because of the higher wax content.
• Minimal delamination, even after tapes have been on for awhile
• Holds edges very well but would be susceptible to damage because it’s that much softer.
• Painting is no problem providing a water based primer is used. When painted with the stripcoat, which is a solvent based material a certain amount of reaction was noticed in the form of minute bubbles.

Kolb TecClay

• Of the three clays Kolb is very soft compared to Chavant and Faber. This version was known as TecClay Hard but still proved to be the softest of the three.
• very consistant in color and was not effected by oven age.
• Kolb was the lightest in weight compared to Chavant and Faber.
• The color was the lightest of the three being a yellow/brown which I’m not use to but it did have very good light/shadow properties.
• I found that it had a tendency to be on the dry side, crumbling between the fingers when manipulated.
• Edges can be a problem because of the dryness but once attained hold up very well.
• Less abrasive than Chavant, about the same as Faber and finishes very well.
• Easiest of the three clays for packing but does suffer from shrinkage if applying in a large thickness, all at once. Behaves better if applied in layers.
• Very crack resistant but only a scale model to evaluate.
• Machines well with little tool abrasion.
• Lower heating temperature than Chavant but like Faber is softer and less dense.
• Painting was not a problem with water based primer but like Faber reacted with the solvent based stripcoat with minute bubbles.

Well as you see, each clay has it’s high points and low points, with no one clay totally outshining the other. To pick one as the overall winner would be impossible, each one is still trying to perfect its product. If there is any rationale in picking the right clay then maybe geographical location would be the answer, go with the material that is produced locally, at least the transportation cost would be cheaper.