Everything You've Always Wanted to Know About Polyform Clay ;o)

Well, maybe not quite everything, but Angela's (aka CraftyGoat's) most recent blog entry does bring up some interesting points. She shares her notes from a Q&A session Polyform offered at the IPCA retreat, so this is very fresh information. I highly recommend giving it a look, if you haven't already-- especially if you regularly use any of the Polyform clays (SculpeyIII, Premo, Studio by Sculpey, etc.).

I was surprised to read that Premo no longer contains phthalates. I'd heard that Kato Clay had made the switch, but nothing about (most of) Polyform's lines of clay. I'm not sure how I feel about that. If the phthalates really were a significant health risk, then of course it's good to avoid them, but I always wonder how much things of this nature may be blown out of proportion. I also wonder how much of a reduction in shelf life we should expect, now that so many brands are going phthalate-free... (This makes buying in bulk and/or stocking up during clay sales seem a bit more risky. Better get busy using up some of my more recently stock-piled clay, huh? (g))

It was also interesting to read that the recommended temperature is a little bit lower than what you need for optimum strength. (Apparently the manufacturers prefer to err on the safe side. Can't really blame them there, but it's good to have the facts.) I guess people knew what they were talking about, all these years, when they've said you're ok if you don't go over 300 degrees. I know I often find my oven's temperature tends to creep up higher than 275, but I've only scorched something once, and that was because it was too close to the heating element.

Anyway... Good stuff to know! Thanks for sharing the info, Angela!

Curing in Stages

As I was working on something at my clay table, recently, it occurred to me how much of my work is cured in stages. I can't recall how long it took me to give multiple curings a try, but it has proven to be nearly essential for what I do.

Even if you're fairly new to polymer clay, you've probably read that it's possible to cure things in stages-- to adhere raw clay to cured (baked) clay and put the piece back into the oven-- but you may not see why you'd ever want to do that. After all, it takes time to cure and wait for a piece to cool, and we're all about instant gratification, these days. For many projects, a single curing is all you need. However, there are times when curing in stages is very much worth the extra time and effort involved.

Here are a handful of reasons to consider curing polymer clay pieces in stages:

• Ease of Handling. Keeping clay free of fingerprints, nail marks, and other undesired textures can be a challenge-- even when wearing latex gloves (which can themselves leave textures and marks). Pre-curing a portion of your project-- a base, for example-- gives you a firm handle by which to hold and rotate the piece while you work on the remainder of it.
• Preventing Dust. As long as clay is "open"-- that is, uncured or raw-- it seems to act like a dust magnet. Even if you're careful about covering uncured pieces between claying sessions, it's common to find stray bits of dust, fluff, and so on that have somehow landed on your project. Removing them can be tedious. Whenever possible, you can prevent dust from ruining your work "so far" by partially curing it. Dust may still settle on cured pieces, but it's easy to wipe away when you're ready to recommence work (or play).
  
• Setting the Plasticizers. One of the reasons we condition polymer clay before sculpting it is to be sure that the plasticizers (the chemicals that make the clay malleable) are evenly distributed through the clay. You may have read (or noticed on your own) that even after clay has been conditioned, it can return to its original (right out of the wrapper) firmer state after it's been sitting around for a while. This is because the clay has cooled and the plasticizers have settled. It's a simple matter to recondition a ball or slab of clay-- just roll it through the pasta machine or scrunch and roll it between your hands. However, it's not such a simple matter to recondition clay that has been formed into a special shape and left to sit for weeks or months. You may cure such a piece and never have a problem, but some suggest that, if the plasticizers settle to the bottom of the clay, the strength of the clay may be reduced. Particularly if you plan to sell or give your work as gifts, you want to be certain that it is as strong and durable as possible. For this reason, I personally prefer to "set" the plasticizers in place by curing sooner rather than later. (When I've neglected to pre-cure, I've even scrapped partially constructed pieces-- putting the clay back to the recondition step-- rather than risk a weaker finished product.) Once cured, pieces can wait weeks, months, or even years for you to get around to the next step in your process.
• Ease of Cleaning/Working on a Solid Surface. For some techniques, I find that a solid surface (cured clay) is easier to work with than a soft one (uncured clay). For instance, when I make faux ceramics, I prefer pre-curing the textured "base" before applying the tinted liquid clay. This makes it easier for me to handle without fear of leaving fingerprints. It also means I can more easily wipe away the liquid clay, should I change my mind after applying it.
  

If you do decide to try curing in stages, there are a couple of things to keep in mind.

First, you'll have to decide, on a case by case basis, whether you trust the adhesion between the raw and cured clay to be sufficient. In many cases, it will be. However, when adding larger pieces-- or when the raw and cured clay share only a small surface connection-- you'll probably want to give the connection a little boost. You can use a dab of liquid clay (translucent, usually, but not necessarily) between the raw and cured clay. (Once cured, the liquid clay strengthens the bond between pieces.) You could also add a mechanical joint, such as a twisted piece of wire cured into the first piece and embedded into the second. Another option is curing the second (or third, or fourth) piece of clay separately and attaching it later (after everything has cooled to room temperature) with a cyanoacrylate glue (super glue).

Second, depending on your project and your plans, you can choose either partial curing (curing just long enough to firm up the clay and prevent it from taking fingerprints or dust) or complete curing (curing to the full length of time recommended by the manufacturers for the size of the piece). Partial curing is of course faster, and if you're going to finish the project and re-cure quickly, it's a perfectly good option. Also, there is less risk of color shifting than if you cure the "base" twice the required length of time. (You can reduce color shifting by using an aluminum foil "tent" over your pieces when you cure them and by mixing a little white or other opaque color of clay into colors that tend to shift.) On the other hand, complete curing makes the piece stronger-- less likely to break during any stresses it may encounter prior to final curing. If you plan to leave the piece for a very long time before returning to complete it, it may be wise to cure it completely. I've read horror stories about (accidentally) partially cured clay eventually crumbling (supposedly under the "attack" of unset plasticizers). It's up to you to decide which option is best for your particular set of circumstances.

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I think that covers the basics. If you've never tried curing in stages, maybe it's time!

Fimo's suggested curing temp. has changed!

I'm more of a Premo gal, myself, but I do have some Fimo in my stock (mostly the translucent that's supposed to be prone to plaquing, for use in faux stone), and maybe someone who reads this will find the information helpful...

Fimo has officially changed its recommended baking/curing temperature-- lowered it from 265° F to 230° F! That's a pretty drastic change! Fimo has always suggested a slightly lower temperature than some other clays, but before, the difference was only 10° F. Now there's a whopping 45° F difference.

This new recommendation is showing up on the newest packages of Fimo. Apparently, the company is indicating that this is an energy-saving issue that they took into consideration when planning the formula for the new recipe of Fimo Soft, which hit the shelves last year.

However, the word is that even older packages of Fimo-- those that don't bear the "new and improved" labelling with the temp. change-- should also be cured at 230° F. (Well, I know they "can" be, but I'm not sure if they go so far as to say that you "should" use the lower temperature...) All types of Fimo brand clay can/should? be cured at the new temperature, including Fimo Classic and Puppen Fimo.

It's a bit confusing, somehow, and disorienting... One of the Great Truths of Polymer Clay-- that different brands can be "mixed and matched" at will-- has been shaken, if not collapsed. Because... if I mix some of my Fimo translucent with some of my Premo violet, for instance, I'll have to decide what temperature to cure it at. Before, I would've set it to 275° F and never thought twice. Now... I'm just not sure! Maybe 275° F is too high. Will it scorch the Fimo? Weaken it? But then what about the Premo component? Will it cure properly if it doesn't get the higher temps?

(...holds head in both hands, rocks back and forth, and mumbles incoherently...) ;o)

Ok, so I'm dramatizing things a bit. (g) It is one more thing to keep in mind.

If you want to read more about this, here's a link to Crafty Goat's blog post on the subject. She has a link to an e-mail conversation between Garie (a polymer clay teacher and artist) and the company that manufactures Fimo brands of clay.

You never know what mind-blowing event will take place next in the ever-evolving world of polymer clay! ;o)