What is a Rainbow Effect? Light Spectrum Observed
The rainbow effect in holograms is the brilliant, iridescent display of spectral colours – red, orange, yellow, green, blue, indigo, violet – that appears when white light strikes the microscopic diffraction grating on a hologram’s surface. Unlike a natural rainbow (caused by water droplets refracting sunlight), the rainbow effect in holograms is produced by diffraction: light waves bend and spread as they pass through or reflect off the tiny grooves (typically 500–2000 lines per millimetre) embossed on the holographic film. Because different colours (wavelengths) of light diffract at different angles, white light (which contains all colours) is split into a visible spectrum that shifts as the viewing angle changes. This dynamic colour shift is a key overt security feature – anyone can tilt a hologram label and see the rainbow effect, instantly distinguishing a genuine hologram from a counterfeit sticker (which appears flat or dull). The rainbow effect is the most recognisable characteristic of embossed holograms, used on credit cards, banknotes, product authentication labels, and security seals worldwide.
🔍 The Science Behind the Rainbow Effect: Diffraction
Diffraction is the bending of light waves around obstacles or through narrow slits. A hologram’s surface contains a diffraction grating – thousands of parallel, microscopic grooves per millimetre. When white light hits the grating:
- Each colour (wavelength) is diffracted at a slightly different angle (red bends the most, violet the least).
- The diffracted light spreads out into a spectrum – the rainbow.
- As you tilt the hologram, the angle between the light source and your eye changes, so you see different colours.
The spacing of the grooves determines the colour dispersion. Closer grooves produce a wider spread of colours; wider grooves produce a more concentrated spectrum. In security holograms, the grating spacing is optimised for maximum brightness and colour visibility.
🛡️ Rainbow Effect vs. True Color Holograms
- Rainbow effect (diffractive) – Produces a continuous spectrum (rainbow colours). Does not attempt to reproduce realistic colours. Most common on security labels and credit cards.
- True color hologram – Records and reconstructs natural colours (e.g., skin tones, green leaves) using multiple laser wavelengths (RGB). More expensive, used for high‑security documents.
🔐 How the Rainbow Effect Serves as Overt Security
The rainbow effect is a highly effective overt security feature because:
- Immediate recognition – Consumers instantly associate the shifting rainbow colours with authenticity (e.g., credit card holograms).
- No tools required – Tilt the label under any light to see the colour shift. No UV lamp, magnifier, or app needed.
- Difficult to counterfeit – Printing a rainbow sticker is possible, but a printed rainbow is static and flat. A genuine diffractive rainbow changes with tilt and shows depth.
- Combines with other effects – The rainbow effect can be layered with microtext, 3D depth, or kinetic motion for enhanced security.
📦 Rainbow Effect in Different Types of Holograms
- Rainbow / 2D holograms – Flat image with pure rainbow colours. Simplest and most common.
- 2D/3D holograms – Multiple layers at different depths; each layer shows its own rainbow colours, creating a dynamic 3D effect.
- Dot matrix holograms – Pixelated gratings that can produce rainbow colours with additional kinetic effects (rolling bar, rotating star).
- DOVID (kinematic) holograms – Combine rainbow colour shift with image switching and animation.
🏭 How Rainbow Effect Holograms Are Made
- Master origination – A laser records an interference pattern on a photoresist plate. A single laser wavelength is used, creating a grating that will produce rainbow colours when viewed in white light.
- Nickel shim electroforming – The master is used to produce a nickel shim (stamper).
- Embossing – The shim presses the grating into metalized PET film under heat.
- Metalization – A thin layer of aluminium is vacuum‑deposited to reflect light through the grating, making the rainbow effect visible.
🌍 Examples of Rainbow Effect in Everyday Products
- Credit / debit cards – The classic Visa dove or Mastercard globe hologram shows a rainbow effect when tilted.
- Indian rupee banknotes (₹500, ₹2000) – The holographic patch with the Ashoka Pillar shows a colour‑shifting rainbow effect.
- Pharmaceutical cartons – Many medicine boxes have a rainbow hologram label that patients tilt to verify authenticity.
- Electronics packaging – Laptop and smartphone boxes often include a rainbow hologram seal.
- Luxury spirits – Whisky bottles with a rainbow hologram strip on the cap.
🔍 How to Verify a Rainbow Effect Hologram (For Consumers)
- Hold the label under any light source (sunlight, desk lamp, phone flashlight).
- Tilt the label left‑right and up‑down.
- Observe the colours shifting smoothly from red to green to blue.
- A genuine rainbow hologram will show vibrant, continuous colours. A fake may look dull, static, or have only two colours.
🌍 Holoseal’s Rainbow Hologram Labels
We supply high‑quality rainbow hologram labels for brand protection and authentication. Our products include:
- Rainbow 2D hologram labels – Cost‑effective, bright colour shift. Ideal for consumer goods, electronics, and promotional items.
- 2D/3D rainbow hologram labels – Adds depth perception to the rainbow effect. Suitable for premium products and pharmaceuticals.
- Rainbow holographic strips and foils – For document security and hot stamping.
- Custom rainbow designs – Your logo or pattern embedded with rainbow diffraction.
We serve clients across Mumbai, Delhi, Bengaluru, Chennai, Hyderabad, Pune, Ahmedabad, Kolkata, Surat, Kochi, Jaipur, Lucknow, Nagpur, Indore, Vadodara, Ludhiana, Patna, Guwahati, Chandigarh and worldwide. With 15+ years of experience, we help you select the right rainbow effect intensity and durability for your product.
❓ Frequently Asked Questions About the Rainbow Effect
Is the rainbow effect the same as a colour‑shift ink?
No. Colour‑shift ink (OVI) changes between two or three colours (e.g., green to magenta) and does not show a full rainbow spectrum. The rainbow effect from a hologram shows a continuous range of colours.
Can a smartphone flash show the rainbow effect?
Yes – a point light source like a smartphone flash is excellent. The rainbow colours will be bright and crisp when you tilt the hologram.
Will the rainbow effect fade over time?
The rainbow effect is caused by physical embossing, not dyes or inks. It will not fade. However, the metal layer (aluminium) may oxidise if not protected, which can dull the overall brightness. A clear top coat prevents this.
Why do some holograms show only two or three colours instead of a full rainbow?
The grating spacing determines the colour spread. Some holograms are designed with specific colour effects (e.g., a gold‑to‑green shift) by using a narrower range of grating frequencies. Others (like security holograms) use a wide range to produce a full rainbow for maximum overt visibility.
Can I get a rainbow hologram with my brand logo?
Absolutely – we create custom rainbow hologram masters with your logo, text, or pattern. The rainbow effect will illuminate your design.
How to order rainbow hologram labels from Holoseal?
Provide your artwork, desired label size, quantity, and any additional features (tamper‑evident, UV, serialisation). We will produce samples for tilt testing before mass production. Contact us for a quote.