How to make a Hologram

Overview

The video is a step-by-step guide to creating a DCG (dichromate gelatin) hologram, covering:

• Selecting and cutting the correct float glass
• Preparing and sensitizing a gelatin emulsion
• Coating and controlling humidity/temperature
• Laser exposure with a reference beam angle
• Chemical development, fixing, and washing
• Alcohol stabilization and drying
• Scraping, sealing, and edge grinding to protect the hologram from moisture

A major theme is process control—especially glass orientation, environmental conditions, and avoiding bubbles/dust. The video also includes practical workshop build details such as gloveboxes, an exposure rig, and drying cabinets.

---

Artistic techniques / creative processes shown

DCG holography workflow

Turning a laser interference pattern into a visible hologram through gelatin chemical processing.

Material selection and orientation

• Using float glass (not specialty optical glass)
• Checking internal manufacturing line patterns
• Choosing the orientation that minimizes scatter—specifically the direction showing “parallel lines”

Emulsion formulation and tuning

• Mixing gelatin + water + ammonium dichromate (sensitizer)
• Adjusting based on laser color:
  • green vs blue performance differences
• Controlling:
  • gelatin temperature
  • dissolution time
  • environmental conditions (around 24°C and ~60% humidity)

Coating aesthetics / quality control

• Veil coating, followed by spin coating for even thickness
• Drying with infrared to manage emulsion behavior and final quality

Interference exposure setup

• Custom exposure stage using reference beam geometry (Denisjuk-style)
• Reference beam angle roughly 45–56°
• Polarization filtering to reduce reflections and increase transmission

Development and stabilization practices

• Time-controlled fixing based on disappearance of dichromate-yellow
• Stepwise alcohol baths (water-to-alcohol exchange)
• Timing cues (including “snake-skin” behavior) to prevent emulsion collapse

Fringe cleanup and edge refinement

• Marking/scraping with spacers to remove unwanted regions
• Precision cutting and smoothing for clean hologram borders

Archival-like preservation approach

• Sealing with epoxy + cover glass in a dust-controlled laminar flow environment
• Addressing DCG’s moisture sensitivity (hygroscopic failure risk)

Final presentation safety

• Chamfer grinding sealed edges using progressively finer bits

---

Step-by-step process

Step 1: Checking the glass (orientation test)

1. Shine an expanded laser beam at a steep angle through float glass.
2. Rotate the glass to identify whether the pattern shows:
   • parallel lines, or
   • wood grain
3. Choose the orientation that shows parallel lines.
4. Mark the direction with an arrow.
5. Cut plates slightly taller than wide so the orientation is easy to remember.

Step 2: Cutting the glass

• Use float glass.
• Lubricate the cut line with kerosene (evaporates, leaving minimal residue).
• Score with a glass cutter using steady pressure and a clean hissing sound.
• Break quickly after scoring; make shorter cuts first.
• Inspect for defects by shining red LED light through.
• Note: scratched plates can be repurposed later as cover plates.

Step 3: Cleaning the glass (removing residue + preventing coating issues)

1. Wash with warm water + window cleaner.
2. Soak in ~3% hydrochloric acid solution:
   • at least 20 minutes
   • no more than 12 hours
3. Scrub with dish soap/sponge and identify the rough side (tin-contact side).
4. Store plates angled with rough side down.
5. Rinse with deionized water.
6. Dry in a warm, filtered drying cabinet (around 30°C+; dust-free air).

Step 4: Preparing gelatin emulsion (gelatin + dichromate recipe)

Example “green laser optimized” batch:

• 367 g cold water
• 68 g gelatin
• 8 g ammonium dichromate (added later)

Process:

1. Heat water bath to 40°C.
2. Dissolve gelatin slowly, stirring every ~5 minutes for about 1 hour.
3. Cool/rest for 12 hours.

Warnings / environment:

• Do not exceed 50°C (overheating ruins the batch).
• Recommended conditions for DCG: ~24°C, ~60% humidity
  • warmer → holograms trend redder
  • colder → greener
• Larger plates may require thicker emulsions (more gelatin).

Step 5: Sensitizing (adding ammonium dichromate safely)

1. Warm gelatin back to ~40°C.
2. Handle dichromate using a glovebox/airlock.
3. Add 8 g ammonium dichromate.
4. Mix ~10 minutes with gentle low heating/stirring.
5. Filter using coffee filters (thermal insulation with foil cover).
6. Fill into a coating squeeze bottle.
7. Remove bubbles using an ultrasonic bath (~1 minute).

Step 6: Coating the glass

• Coat inside a controlled glovebox environment:
  • ~24°C, ~60% humidity, dust-free
• Place the clean plate into a tray to catch drips.
• Apply one continuous “veil” coating motion around the edges.
• Spin coat:
  • turntable ~80 rpm
  • 1 minute, then infrared drying for ~5 minutes
• Dry in a cabinet:
  • at least 12 hours before exposure
  • keep ~24°C and ~60% humidity
  • avoid “milky” moisture traps

Step 7: Building the exposure setup

• Create stable feet using flattened/sharpened nails (3-point stability).
• Use a model (3D silver print) glued to a glossy white brick with spacers.

Laser path elements:

• polarization filter (rotatable)
• mirror redirection
• concave mirror expansion

Reference beam geometry:

• Use alignment methods (“sundial-like” adjustment).
• Plan Denisjuk-style exposure:
  • reference beam angle ~45–56°
  • verify with a protractor

Step 8: Exposure (laser recording + environmental control)

1. Recheck emulsion and glass; clean underside if needed.
2. Cut plates into smaller sections using tape spacers.
3. In light-tight conditions, maintain:
   • humidity ~60%
   • temperature ~24°C
4. Place plate emulsion-side-down.
5. Use masking tape to avoid exposed regions from internal reflections.
6. Secure plate with magnets over painted/spaced components.

Mentioned exposure parameters:

• ~100 mW green diode laser (533 nm)
• exposure time: 4 minutes
• dark reaction: 5 minutes (can extend; may increase brightness)

Practical notes:

• DCG can be forgiving: overexposure and delayed-development scenarios are described.
• Blue lasers are far more sensitive for DCG (stronger light response).

Step 9: Developing, fixing, washing, and drying

Safety:

• Use a recommended respirator with charcoal filters and strong ventilation.

Fixer:

• Use Tetenal Superfix, diluted 1:3 (fixer:water), at ~24°C
• Stop when dichromate-yellow disappears (time depends on emulsion age/freshness)

Wash:

• Water bath for 1–20 minutes depending on size

Alcohol stabilization (anti-collapse exchange):

• 54% → 59% → 84% → 100% isopropyl alcohol
• timing cue: ~25 seconds each for small plates
• key cue: stop evaporation progression when the emulsion looks like “snake skin” at each transition

Drying:

• warm, dry air:

  • 30°C

  • < 20% humidity
• use a paint stripping gun at low airflow/high heat
• “L-motion” drying and finishing in circles
• observable behavior:
  • becomes milky, then returns to transparency
  • appears after ~2 minutes, then continues drying (~3 minutes more)

Storage:

• airtight container + silica gel

Step 10: Scraping (removing unwanted gelatin + shaping edges)

Safety and preparation:

• Wear a respirator; prevent condensation on the hologram.

Edge/fringe refinement:

1. Mark a rectangle frame and centerlines with a pen.
2. Sponge-dampen edges to remove brittle gelatin with a ~5 mm safety gap.
3. Razor-blade rough removal repeated around all sides.

Precision edge work:

• Steel ruler at 45° with clamps
• Swab with 100% isopropyl alcohol
• Cut emulsion near the line with a new razor
• Remove strip with blade flat

Final: smooth edges.

Step 11: Sealing (protect from moisture to preserve visibility)

Why sealing matters:

• DCG is hygroscopic; moisture causes swelling and fringe collapse → invisibility.

Sealing environment:

• Dust-free laminar flow bench (self-built straw airflow wall).

Epoxy assembly:

1. Mix 2-part epoxy resin per manufacturer ratios.
   • example: 12 g resin + 6.6 g hardener
   • warm mixing helps flow
2. Use a plastic cup spout for controlled pouring.
3. Clean/dry cover glass (prefer same thickness to reduce differential expansion).
4. Pour epoxy in a T-shaped distribution.
5. Gently heat to reduce bubbles.
6. Lower cover glass slowly to avoid new bubbles.
7. Use corner contact supports with saran wrap-wrapped cinder blocks.

Cure and cleanup:

• cure for at least 24 hours
• avoid extra pressure to prevent visible force lines
• remove excess glue droplets afterward (isopropyl alcohol + razor)

Step 12: Grinding (safe, presentable chamfered edges)

Tools and precautions:

• Use glass grinder (Kristall 1) with interchangeable bits (rough → medium → fine).
• Wear goggles + respirator.
• Optionally tape/protect surfaces.

Chamfer method:

1. Grind top/bottom edges first at 45°.
2. Final pass level to remove the triangle tip and reduce chipping risk.
3. Repeat passes until edges are smooth.
4. Remove protective tape.

---

Creators / contributors mentioned

• Swann Rack (main creator/instructor)
• Miro (brother; helped make the video)
• Stefan (friend; helped make the video)