“Cel” originally meant celluloid—thin sheets of cellulose nitrate plastic (historically called “celluloid”) plasticized with camphor. Early studios used nitrate because it was transparent, flexible, and available from the motion-picture supply chain. But nitrate is highly flammable and chemically unstable, so the industry sought safer bases.
Studios adopted cellulose diacetate (CDA) first, then cellulose triacetate (CTA)—clear, stable enough for production, and easier to paint/ink than polyester. However, acetate is an ester and can hydrolyze (the “vinegar syndrome”), especially at higher temperature and humidity; storage guidance emphasizes cool, controlled RH.
By the late 20th century, some cels and overlays used polyester (PET/Mylar), which is mechanically/chemically stable. But its polished, low-energy surface doesn’t wet well with traditional gum-based paints; studios often preferred synthetic paint systems when using PET.
The adoption of computer-assisted ink/paint pipelines in the 1990s effectively ended the use of production cels at major studios—so the modern “material” is often none (digital). This also explains the contraction of new cel supply post-1990s.
Celluloid = cellulose nitrate (camphor-plasticized); cellulose acetates = safety film (diacetate/triacetate). Dealers sometimes write “celluloid acetate,” but for preservation we keep the terms distinct: nitrate (oxidative hazards) vs. acetate (hydrolytic VS).
Differences arise from: (a) chemical substitution on cellulose (nitrate vs diacetate vs triacetate), (b) additives (plasticizers/stabilizers, e.g., TPP, DEP, DMP, triacetin, camphor ), (c) physical packing (crystallinity/free volume), and (d) surface energy.
These shift Tg, water diffusion, clarity, paint adhesion, and sensitivity to temperature/RH.
| Material | Production years / typical use | Studios / usage examples | Key differences (what you notice) | Underlying drivers (why it happens) | Preservation concerns (real-world risks & failure modes) |
|---|---|---|---|---|---|
| Cellulose Nitrate (CN) | Film: 1889–early 1950s; painted animation cels only limited/early use due to safety | Early cinema stock; Early Disney (e.g., Snow White and the Seven Dwarfs, 1937) before switching to acetate in the early 1940s; avoided later due to flammability and handling regulations. | Extremely flammable; yellows/embrittles; odor distinct from vinegar | Nitro-ester groups are energetic; oxidative pathways dominate; historically camphor-plasticized | Fire hazard; spontaneous heating risk; fragmentation; specialized cold storage and limited handling required |
| Cellulose Diacetate (CDA) | 1920s–1940s (animation transition from nitrate) | Early Disney/other studios during nitrate→acetate changeover | Softer/more flexible than CTA; can yellow/haze earlier | Lower DS (~2.0–2.4) → more polar; higher water uptake; often higher plasticizer load | Early haze, warp/shrink with plasticizer loss; adhesive/paint interactions vary; sensitive to warm/humid storage |
| Cellulose Triacetate (CTA) | 1930s–1990s (dominant cel base) | Disney, Toei, Ghibli, most anime houses mid-century onward | Excellent clarity/stability when new; susceptible to vinegar syndrome (VS) over decades | Higher DS (~2.7–3.0) → more hydrophobic than CDA; still hydrolyzes (acetic acid generation) | Vinegar odor, shrinkage/warping, stuck paint; boundary-layer effects in frames; needs cool temps and controlled RH to slow VS |
| Polyester (PET/Mylar) | 1970s–2000s (overlays; some late cels); common in conservation materials | Xerography overlays; preservation/backing | Very stable chemically; excellent clarity; low water uptake | Non-polar aromatic polyester; low surface energy → poor paint wetting with traditional systems | Paint adhesion failure/peeling; static issues; otherwise robust—good for overlays but not ideal for classic cel paint without modified binders |