How to remove creases from old prints, including Hiroshi Nagai works

Assess the print’s medium and condition

Before intervention, identify whether the print is an offset lithograph (common for Nagai’s commercial works, 1970s–80s) or a screenprint, as the former’s thinner paper (90–150 gsm) and oil-based inks respond differently to moisture than archival giclée prints (250–310 gsm cotton-rag). The Metropolitan Museum of Art notes that offset lithographs often use mechanical, not hand-laid, paper—prone to embrittlement over time.

Examine for ink cracking along crease lines; if present, humidification risks further damage. For glossy finishes (common in Nagai’s travel posters), surface tension may mask minor creases until viewed at an angle—test with raking light. Matte finishes, conversely, diffuse light and can obscure superficial wrinkling until framed under UV-protective glazing.

Humidification and flattening methods

For stable prints, use a humidification chamber: place the print between two sheets of acid-free blotter (e.g., 250 gsm conservation-grade) lightly dampened with distilled water, then weight it under a 2–3 kg (4.5–6.5 lb) board for 24–48 hours. Avoid direct water contact; the Smithsonian American Art Museum’s conservation guidelines warn that excessive moisture swells paper fibers irreversibly in lower-grammage stocks.

For persistent creases in 150–200 gsm paper, professional dry mounting (heat-activated adhesive to an acid-free substrate) may be viable—though this is permanent and reduces long-term value. Expect costs of $120–$300 USD per print, depending on size (e.g., 50x70 cm / 20x28 in). Never attempt ironing or steam, even on low heat; the combination of pressure and moisture distorts inks and compresses paper fibers.

Framing as a preventive measure

Once flattened, frame the print with acid-free conservation matting (4-ply, 100% cotton-rag) and UV-filtering glazing (e.g., 99% UV-blocking acrylic, 2–3 mm thick). The Fine Art Trade Guild standards recommend a 5–10 cm (2–4 in) mat border to prevent contact with glazing, which can reintroduce static-induced wrinkling in dry climates.

For standard sizes (e.g., 30x40 cm / 12x16 in or 50x70 cm / 20x28 in), expect framing costs of $250–$600 USD, including archival materials. Hang prints at a center height of ~145 cm (57 in) to minimize handling-related stress, and adhere to the two-thirds rule above furniture to reduce airborne particulate exposure.

When to consult a professional conservator

Seek expert intervention for prints with:

• Ink flaking or silvering (common in offset lithographs with metallic pigments).
• Acid burn or foxing (brown spotting) indicating prolonged exposure to non-archival mats.
• Creases intersecting signed or editioned margins (e.g., Nagai’s lower-right signatures).

Conservators use localized solvent vapor (e.g., ethanol mist) to relax fibers in high-value works, followed by Japanese tissue repairs for tears. Costs range from $400–$1,200 USD for mid-century prints, excluding framing. The National Gallery of Art’s print department emphasizes that DIY methods (e.g., book pressing) risk setting creases permanently in aged paper.

Long-term storage and handling

Store unframed prints flat in solander boxes (pH-neutral, lignin-free) or vertically in archival sleeves (polypropylene, 4–6 mil thickness). Avoid PVC-based portfolios, which off-gas plasticizers that embrittle paper. For Nagai’s glossy posters, interleave with glassine (not wax paper) to prevent ink transfer during stacking.

Handle prints by edges only, using nitrile gloves to prevent oil transfer. Rotate displayed works annually to limit light exposure; even UV-filtered glazing permits 10–15% light transmission, accelerating fading in aniline dyes (common in pre-1990 commercial prints). Climate control is critical: maintain 40–50% relative humidity and 20–22°C (68–72°F) to prevent cyclic expansion/contraction.