The APTII products page at http://www.apt2products.com/porcelain.htm says
"acrylic emulsion additive that is food safe and non-toxic. It cleans up with water and has an indefinite shelf life." and " APT-II Enhancer will thicken all brands of slip and clay bodies, enabling the ceramist to attach, mend and create surface decorations."
Thus one might infer that it is a mixture of several ingredients that would include at least water, an acrylate polymer, and an emulsifying agent. An arylic polymer is a polymer of 2-propenoic acid,
You should be able to look up on the web where the main infra-red peaks are located.
My book, "Dispersing Powders in Liquids" (Elsevier, 1988) mentions polyacrylates as dispersing agents but does not include the infra-red spectrum.
One thing you could do to get a better spectrum is dry your sample. Most likely this polymer is dispersed in water hence the giant peak distorting the graph a bit at the 3500 range. Maybe cure/dry the polymer film on a piece of glass or silcon wafer overnight in an oven, and then take a spectrum with your dry film.
In order to recognize the structure of chemical compound, FT-IR can not be that much helpful, for this 1D and 2D NMR along with Mass spectroscopy and IR could give you a solid idea. But usually IR to for confirmation, for example, here you already know about the general compound containing Acrylic acid, now you can confirm the peaks at 1800 and 2500 for carbonyl and carboxylic respectively. This is what I ask my student to do in similar cases, scan the sample, get the spectrum, write down their guess (which they already may know in this case, Acrylic) then assign the peaks they see as much as possible. Remember the fingerprint area (below 1200nm) we are not interested in it, as there is a lot of overlapped peaks overthere. Hope this works for you. Let me know if you have any more questions.