When we make things from polymer clay, there will always be a time when we need to bond polymer clay to itself. Whether you attach raw to raw, raw to baked, or baked to baked, you’ll need to know some technical things in order to get the best bakeable bond. It’s commonly suggested that you should use a product, such as liquid clay, as a sort of bakeable glue when bonding polymer clay to itself. But is this truly necessary? And if so, which product works best? I sat down in my studio with all my clay brands and bakeable glue products and here’s what I found.
Bonding Polymer Clay - Summary
Before I get into the details, here’s the gist of what I found. I was honestly surprised, btw.
- The clay brand matters when bonding polymer clay to itself.
- Use a bonding agent when bonding either raw or baked clay to baked clay.
- Premo, Souffle, and Kato bonded poorly to themselves unless a bonding agent was used, even raw to raw!
- Cernit bonded to itself well, raw to raw, but not raw to baked.
- Fimo Professional bonded well to itself whether raw, baked, or using a bonding agent.
- Raw Premo didn’t bond well to baked Premo unless Fimo Liquid was used. The same was true for Kato Polyclay.
- Raw Souffle bonded well to itself with a bonding agent, but no bonding agent allowed a strong bond between raw and baked Souffle. In fact, baked-to-baked fared better than raw-to-baked (with a bonding agent).
- The best bonding agent in these tests was Fimo Liquid. (Yes, better by far than Sculpey Bake and Bond.)
- All brands of liquid clay bonded better than Kato PolyPaste.
- The best way to bond baked to baked is to use Genesis Thick Medium with a raw clay bridge.
- This is not an exhaustive test. Your results may vary! But it should give a general guideline. Note the recommendation for each category, below.
Bonding Polymer Clay to Itself
To test the adhesion of bonding polymer clay to itself, I created a series of test tiles in five brands of polymer clay. Circles of the same clay were applied to the test tiles raw, baked, without any glues, and with bakeable glues.
Brands tested were Premo by Sculpey (in black), Souffle by Sculpey (in grape), Kato Polyclay (in white), Cernit Number One (in blue), and Fimo Professional (in true green).
Variations tested were:
- Raw to raw
- Raw to baked
- Baked to Baked
- Baked to Baked with a raw clay bridge
Bakeable Glues or Bonding Agents
It’s generally assumed by most experienced polymer clayers that raw clay bonds well to itself without any sort of assistance from other products. But bonding agents and bakeable glues are generally recommended when bonding raw clay to baked clay or when baking baked clay to another piece of baked clay.
While some products are specifically marketed for this purpose, there isn’t much difference, chemically, between them. They are all variations of liquid clay. Here are the bakeable glues or bonding agents that I tested.
By the way, all of these products are (relatively) fresh and were stirred well (except for the two gels in pots). Always make sure you stir your liquid clays, especially Sculpey Clear and the Lucy Clay Glassymer clays.
Bonding Raw Polymer Clay to Itself
In this experiment, I pressed a circle of raw clay to a tile of the same brand of raw clay. I tried it “naked” with no products and also with each of the bakeable glues you see above. I pressed firmly, but did not blend the edges the way you typically might do when sculpting or building up a sculpture. I did use alcohol to remove oils before bonding and did not “scuff up” either clay.
I was quite surprised to find that in the case of Premo, Souffle, and Kato, the bond of just the raw clay to itself was not as strong as when a product was applied as a glue. I could easily flick off the applied clay with my finger, and doing so left no damage to either piece of clay. The bond simply failed.
But when any of the above bakeable glues or bonding agents were used, the bond was strong and nearly impossible to break.
In the case of Fimo Professional or Cernit, the bond was strong whether a bonding agent was used or not.
When bonding raw polymer clay to itself, use any bakeable glue or liquid clay to enhance the bond.
Bonding Raw Polymer Clay to Baked Polymer Clay
On the other hand, when you attach raw polymer clay to baked polymer clay, experienced clayers expect the bond to be poor. It has long been recommended to use liquid clay or Bake and Bond to enhance this bond.
My tests show that this is (sort of) correct. Only Fimo Professional bonded well to itself, raw to baked. All other tested brands fared poorly and could easily be pulled apart without damaging either piece.
However, things got strange after that. In the case of Premo, Kato, and Souffle, the only bakeable glue or bonding agent that worked well to enhance to bond and make it strong was Fimo Liquid. For Cernit and Fimo Professional, all liquid clays worked well.
In the case of Cernit, neither Kato PolyPaste or Genesis Thick Medium created a bond (in raw to baked clay) as strong as the liquid clays did.
When bonding raw to baked clay using Premo, Souffle, or Kato, use Fimo Liquid to enhance the bond. When using Cernit to bond raw to baked, any liquid clay can be used. When using Fimo Professional, baking raw to baked, no bonding agent is needed but any liquid clay can be used.
Bonding Baked Polymer Clay to Itself
So what should you use to bond baked polymer clay to itself? This happens when you need to assemble something after baking or make a repair. If you can’t rebake it, use a gel superglue, such as Loctite Control Gel. But if you can bake it again, what’s the best strategy?
The results pretty much echoed the ones for attaching raw clay to baked clay. Fimo Liquid Gel gave the strongest bond.
But another star comes out here. With all brands of polymer clay except Kato Polyclay, and aside from Fimo Liquid Gel, a remarkably good bond was accomplished with Genesis Thick Medium, but only when used with a bridge of raw clay.
When bonding baked polymer clay to itself, I had good results with Fimo Liquid Gel. I also had good results with Genesis Thick Medium when a bridge piece of raw polymer clay was used.
Bonding with Genesis Thick Medium
Genesis Heat Set Paints are a lovely line of artist’s quality paints made from a vinyl plastisol and work beautifully on polymer clay. They have a thick painting medium as part of their line that has sort of gained a cult following among polymer clayers as an excellent bakeable glue. While I didn’t find that it worked as well as liquid clays when bonding raw to baked polymer, there is something about it that allows bonding to baked clay.
I found (and my tests confirmed) that it makes a really great “glue” when you need to bond baked clay to itself. Just rub a thin layer (seriously thin) on the baked clay and then use a thin snake or piece or baked clay between the pieces. Press together. This will hold with remarkable strength and will not slide or slip. After baking, it’s incredibly strong. Give this a try!
What Are Bakeable Glues?
All of the above liquid clays, bakeable glues, and bonding agents are vinyl plastisols. This just means they’re the same thing as polymer clay, but without the binders that turn polymer clay into a putty. Chemically, they’re all quite similar. All can be applied to or even mixed with polymer clay and then baked to cure. None of these products have anything to do with conventional adhesives such as white glue (PVA), Super Glue (cyanaoacrylate), or E6000.
Lucy Clay Glassymer Glue, Cernit Glue, Sculpey Bake and Bond, and Kato PolyPaste are marketed specifically to be used in this way for bonding clay to itself in a cured bond. However, I see no evidence of them containing any sort of true adhesive or glue.
In the case of Sculpey Bake and Bond and Kato PolyPaste, these products are thicker and therefore less likely to slip and slide as you are using them with your project. They stay put better. According to my tests here, however, neither bonds better than the other products. In fact, Kato PolyPaste bonded noticeably more poorly than the other tested products.
Testing this was really hard on my fingernails! Anyway, based on the tests I did here, the conclusions are:
- Use any liquid clay to enhance the bond of raw to raw polymer clay, especially when using Premo, Souffle, or Kato.
- When making a raw to baked polymer clay bond, you’ll get the best results if you use Fimo Liquid Gel to enhance the bond.
- When bonding baked Kato to itself, use Loctite Control Gel. For other brands, use Fimo Liquid Gel or a bridge of Genesis Thick Medium plus raw clay. For Fimo, I don’t think it matters. That stuff bonds like magic to itself.
These results are not exactly what I expected to see. I was surprised to see the poor bonding results with Premo and Souffle in particular. I’ve not noticed that type of problem in my own work. Perhaps this was a fluke. I just tested one color from each brand. Or perhaps in most projects we really don’t need as much of a stringent bond as I was trying to accomplish in these tests. Either way, I think we can safely conclude that we should be using liquid clay to enhance a bond when we need it to be strong. Also, that Cernit and Fimo Professional create stronger bonds when applied to themselves than do the other brands.
I will keep my eyes open for any more observations on this subject and I may revisit it in the future. Also, Phyllis Cahill did similar tests with both glues and some of the same products. Her results were different as night and day from mine. Frustrating!
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