Black and white darkroom photographic paper drying deformation 'flattening and glossing (Ferrotyping & Dry Mounting)' prevents edge wave curling

1. The physical and mechanical tragedy of paper-based photographic paper (FB): the water absorption anisotropy of pure cotton plant fiber

Why is resin-coated photo paper (RC) as flat as a ruler after drying, while cotton-based photo paper (FB) is curled like potato chips?

• Plastic Sandwich Armor for RC Photo Paper:
• RC photo paper is tightly compounded with polyethylene (PE) waterproof plastic layers on both sides of the paper core; moisture cannot enter the inside of the paper core at all, and there is no change in size after drying.
• FB photo paper’s pure natural cotton rag paper base (100% Cotton Rag Paper Base):
• The paper core is an unobstructed pure natural high-density plant cellulose intertwined network;
• During the washing process, the cotton fiber cell wall absorbs water and expands wildly, and the expansion coefficient of the fiber in the transverse and longitudinal directions differs several times;
• The maximum shrinkage rate of the surface gelatin emulsion layer and the underlying pure cotton paper core during the evaporation of water produces a huge tension imbalance shear force**;
• The edge fibers lose external restraint and naturally shrink and gather, causing the dried photo paper to form a serious three-dimensional wavy saddle-shaped curl and distortion.

2. The mirror miracle of traditional chromium alloy plate heating and glazing method (Ferrotyping)

The darkroom master's legendary craftsmanship allows the surface of pure cotton photo paper to present a deep, obsidian-like high-gloss mirror:

• Molecular Memory Reconstruction of Thermoplastic Gelatin:
• Gelatin emulsion in a wet state is thermoplastic (it will soften and flow slightly when exposed to high temperatures);
• Mirror pressing operation of glazing machine:

1. Prepare a mirror polished stainless steel plate (Ferrotype Chrome Plate) that has been polished with aerospace-grade multi-layer chrome plating and has no scratches;
2. Soak the thoroughly washed wet photo paper in diluted wetting agent (Photo-Flo) for 1 minute;
3. The emulsion side (the front side of the drug film) is tightly facing downwards and attached to the absolutely mirror-surface chrome plate;
4. Use a heavy-duty rubber roller (Squeegee Roller) with huge and even downward pressure to crush the photo paper from the center to all sides, completely squeezing out all the air bubbles and excess moisture between the photo paper and the chrome plate;
5. Put the canvas into the heated glazing dryer (temperature controlled at 60℃~70℃ for constant temperature baking);
6. Clear sound of automatic falling off: As the water evaporates, the gelatin molecules adhere tightly to the absolutely smooth mirror chrome plate and harden and shape;
7. The moment the water evaporates completely, the photo paper automatically bounces off the chrome plate with a crisp "pop" sound! The surface of the photo paper has a noble mirror luster that is as flat as polished obsidian glass, with high contrast and amazing albedo!

3. Museum-level flat collection standard: hot-pressed, acid-free dry mounting (Dry Mounting) complete four-step method

In order to make expensive paper-based photo paper permanently flat as a mirror and meet the century-old collection standards of museums, the modern photography industry generally uses the Hot Press Dry Mount Press process:

• Core material: Acid-free hot melt dry mounting film (Dry Mount Tissue):
• An extremely thin special hot-melt film (such as Bienfang Seal / Color-Mount) that is completely non-sticky, neutral and acid-free at room temperature;
• The adhesive film undergoes hot melt flow when heated to 85°C~95°C, and forms an absolutely solid rigid acid-free bond after cooling.
• Professional Four-Step Framing Workflow:
• Step 1: Pre-dry and dehydrate photo paper and acid-free cardboard:
• Put the photo paper and 100% cotton acid-free mounting card into a 90°C hot mounting machine and bake under pressure for 30 seconds to completely evaporate the trace air moisture remaining inside the fiber.
• Step 2: Soldering iron positioning (Tacking):
• Clip the dry mounting film on the back of the photo paper;
• Use a slightly heated dot-shaped handheld soldering iron (Tacking Iron) to gently draw an "X" shape in the center of the back of the photo paper, and fix the adhesive film on the back of the photo paper;
• Use a heavy-duty hob to precisely cut and trim the photo paper flush with the edge of the film.
• Step 3: Align and secure with the acid-free card base:
• Accurately place the photo paper at the golden section of the huge acid-free exhibition cardboard (Museum Board);
• Lift up the two diagonal corners of the photo paper, use a soldering iron to lightly burn two points on the outer edge of the film, and temporarily fix the system to the base plate.
• Step 4: Feed into large vacuum heat laminating machine (The Press):
• Cover with Teflon anti-stick protective release paper;
• Lock into 90℃ constant temperature heat laminating machine and pressurize for 2 minutes;
• Immediately after taking it out, press it hard with a flat and thick marble cold pressing plate and let it cool for 1 minute to allow the hot melt glue to completely solidify;
• Finished Product Effect: The photo paper and the pure cotton card board are completely integrated into a rock-solid body. Whether it is hung in the exhibition hall and exposed to the sun under the strong spotlights, or it has experienced decades of moisture changes, the photo paper always remains as absolutely flat as a knife cutting a steel plate, showing the master's handed down style!

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