When working with steel and stone, it’s not too uncommon to combine it with multitude of other materials. Wood and steel go together like butter and bread. Stone and wood too as the two give a nice accent between the two natural materials. I’m not sure if I’m glad that leathers and fabrics are more familiar as materials than plastics. Nevertheless, it’s better to dip yourself into unknown regions from time to time and do something new. You’ve most likely noticed that I’ve been rather absent from writing posts during the last few weeks, and that’s because I’ve been working on projects that simply took most of my time. One of the projects I just finished was to produce a replica of a cocoa fruit for the local botanical garden for exhibition purposes.
Whether or not the project was a success will be left to dark. The customer was happy and that’s all that matters. Nevertheless I strongly feel that it was my inexperience with resin casting caused more troubles that the final product was ultimately worth, but it’s all a process of experimenting and learning with these kinds of things. While resin casting is very much similar to other forms of casting, sand and vacuum casting being most familiar methods to yours truly, polyester resin has its kinks one can’t really see beforehand before without experience.
The resin used in this project was as mentioned in the title, Artidee’s XOR Crystal Polyester resin. As with other materials like it, it comes in a composite form with the resin as a separate canister and hardener in a glass bottle. You don’t need much hardener with XOR to engage the curing process. This is very similar to stone plaster, in which one of the best ones I’ve had the (dis)pleasure to use required some 3% of the overall volume. There was an incident few years back, where a younger craftsman in training used too much hardener with the stone plaster, causing it to release fumes, heat up to a point that it broke the glass jar he mixed it in. I didn’t try this with XOR, because I doubt the customer would’ve been glad to see their product being completely fucked up by simple curiosity. Nevertheless, the fact is that often adding slightly more hardener than needed can cut hours from the curing time. This is not all too universal, but we all need some sort of placebo at times.
The curing process in XOR requires that its cut from air contact. If it is air cured, then the surface will remain sticky. This is a crux with the resin, and this is something that needs to be taken into notice when selecting the resin you want to use. In principle, it should be pretty easy to cut all air circulation from the plastic, this isn’t always the case without proper built. After handling all sorts of chemical throughout the years, it’s not all too hard to simply see and smell chemicals that would be able to kill you. XOR is one of those, and I intentionally tested using a plastic cover to cut off the air from the casting. The results were that the damn plastic began to bubble and melt even going to the extent of dripping tiny droplets of running acrylic into the casted surface. Now, logic would dictate that it wouldn’t be the best idea to make a mould housing out of plastic, but I just needed to be tested to some extent to know it myself with solid, undeniable proof. It’s for the experience and firsthand knowledge, and nothing can replace that.
With any casting material, the finish is important. The better the finished surface, the less work you need to do with it to make it presentable. In all honesty, the unrefined finish of the XOR is pretty good if your mould has good, smooth surfaces. Depending on the geometry of your mould, the resin may have some difficulties on invading every nook and cranny you have in there. While the resin has arguably a high viscosity, it is more similar to slightly runny honey, so to speak. It can handle high geometry just fine. The cocoa shells are strongly dimensional with high amount of details due to the uneven surface of a fruit. XOR did a good job at replicating each and every of those details.
Of course, if the casting has been in contact with air, it has that sticky surface as mentioned above. In this case, it would better to just take few millimetre layer off with whatever tool you want to use and polish the actually hardened surface. If you’ve ever polished plastic with manual labour, this option may sound absolutely awful. Polishing any plastic is tiresome and one of the dullest jobs out there. Nevertheless, I must say that even with the best possible circumstances the surface of the casting will be slightly cloudy. It’s transparent for sure, but it’s not crystal clear by any means. It would be a good idea to bring some plastic polishing paste of similar with you when casting with XOR, just in case. It’s a whole another matter whether or not you want to actually go through all that polishing, and let’s be frank; you sure goddamn might as well. You’ve put a decent money into this, you might as well spend an evening with a bottle of beer and keep scrubbing the plastic until it shines like Picard’s bald head.
But you know what’s the problem with that? XOR doesn’t really polish well. If the surface isn’t what you wanted when you took it from the mould, you’re going to have some work ahead of you to get it shiny as hell. As my comparison point is with hard materials with stones, gemstones, jewels and different metals, it just might be that I am expecting completely wrong kind of result on how the polished surface should come to.
As with most standard quality resins, XOR is pretty high grade. Obviously not the best of the best, but to say that it works just fine for its price category would be apt. It can take some mechanical stress, but not to the same extent as the harder acrylics. I wouldn’t use this to make gear parts or similar, I would go for harder resins.
That’s the bottom line; for a 20€ resin it does its job, but there are better options out there. It’s good for prototyping and all that, but if you have the chance and budget to go for something better, go for that.
We’ll be back next week, hopefully more in schedule with Monthly Music.