UV

Technically, black lights emit ultraviolet (UV) radiation, specifically in the UV-A range, which spans wavelengths between 315 and 400 nanometers (nm). This type of light is just beyond the visible spectrum that human eyes can detect, meaning it is invisible to us under normal circumstances. However, black lights emit enough visible violet light to create the characteristic “purple glow.”

Here’s a more detailed breakdown:

1. Types of UV Light

• UV-A (320–400 nm): Long-wave UV light is the least harmful form of UV radiation and the type most commonly used in black lights. It is responsible for causing fluorescence in certain materials.
• UV-B (280–320 nm): Known for its more harmful effects, such as sunburn, this type is not typically used in black lights but can damage materials.
• UV-C (100–280 nm): Highly energetic and germicidal, UV-C light is not present in black lights and is usually employed in sterilization processes.

1. Mechanism of Fluorescence

Fluorescence occurs when certain pigments or substances absorb UV light and re-emit it as visible light. This is due to a process where UV photons excite the electrons in the fluorescent materials. These electrons jump to a higher energy state and release energy in the form of visible light upon returning to their average energy level.

• Photon Absorption and Emission: In technical terms, UV photons have more energy than visible light photons. When these photons are absorbed by fluorescent materials (like fluorescent pigments in paint), they cause the material’s electrons to jump to a higher energy level. As the electrons return to their original state, the excess energy is released as visible light.
• Stokes Shift: This is the difference in energy between the absorbed UV light and the emitted visible light. The emitted light has a longer wavelength (less energy) than the absorbed UV light due to energy loss during the electron’s return to its ground state.

1. Black Light Construction

Black lights are typically made using specialized fluorescent lamps or LED diodes that filter out most visible light, leaving mainly UV-A light to pass through:

• Fluorescent black light bulbs: These are similar to regular fluorescent bulbs but use a phosphor coating that primarily emits UV-A light. The tubes are often coated with a filter (Wood’s glass), which blocks most visible light while allowing UV-A to pass.
• LED black lights: Modern black lights often use UV-A emitting LEDs. These LEDs are more energy-efficient, produce less heat, and have a more focused output than fluorescent tubes. They are available in various wavelengths, but those used for black lights typically emit around 365–395 nm.

1. Effect on Acrylic Paints

When black lights illuminate paintings made with fluorescent pigments, the energy from the UV light causes certain pigments to fluoresce and become visible. The strength of this effect depends on the specific pigments used in the paint.

• Fluorescent pigments: These contain compounds such as zinc sulfide or cadmium sulfide, which are highly responsive to UV light. Under black light, these pigments emit light in the visible spectrum, creating a glowing effect.
• Non-fluorescent acrylic paints: These do not fluoresce under UV light, as their chemical structure does not absorb and re-emit UV radiation. However, UV light can still reveal slight imperfections in the paint or varnish, such as underpainting, repairs, or retouching done with fluorescent materials.

1. Degradation of Paints and Materials Under UV Light

UV light, even UV-A, can cause long-term damage to paintings and materials:

• Fading: UV light can cause certain pigments, especially organic pigments, to fade over time. In acrylic paintings, exposure to UV light can result in the breakdown of certain dyes, leading to a loss of color intensity.
• Material Degradation: Prolonged exposure to UV light can degrade other materials used in paintings, such as varnishes, binders, and canvas. In particular, natural fibers in canvases can weaken and become brittle over time when exposed to UV radiation.

Preventive measures often include using UV-filtering glass or acrylic in frames and ensuring that paintings are displayed in environments where exposure to UV light is controlled.

1. Applications in Art Conservation

UV light is commonly used in art conservation to reveal aspects of a painting that are not visible under regular light:

• Identifying Restorations: UV light can reveal areas that have been retouched or restored. Different materials fluoresce differently, making it possible to detect later additions or repairs that would otherwise blend into the painting under normal light.
• Detecting Underpainting: Many artists sketch under their final paintings. Some of these underlayers might fluoresce under UV light, providing insights into the artist’s process.
• Authenticity Verification: UV light can also be used to authenticate paintings. Original works might contain pigments or varnishes that respond in particular ways to UV light, while forgeries might not replicate these exact effects.

1. Lighting Conditions and Artistic Expression

The interaction of black light with fluorescent acrylics opens up creative possibilities:

• Layered Effects: Artists can create paintings with dual effects, one under regular light and another under black light. By selectively using fluorescent pigments, an artist can control which parts of the painting “come alive” under UV light.
• Mood and Atmosphere: Black light can evoke a mysterious, otherworldly atmosphere. In installations or exhibits, black lights are often used to create an immersive experience where the artwork shifts depending on the lighting.
• Poidomani’s Potential Use: For an artist like Humberto Poidomani, whose work addresses complex ideological themes, black light could serve as a tool to emphasize his narratives’ hidden or surreal elements. The focus on social fragmentation and the critical view of modernity could be further explored by manipulating light to reveal or obscure parts of his works, creating a visual metaphor for concealed truths or fragmented reality.

Conclusion

From a technical perspective, black light and UV light offer unique possibilities in art creation and display, particularly when paired with acrylic paints and other UV-reactive materials. Fluorescence under UV light results from a precise interplay of photon absorption and emission, and while the effect can be visually striking, it also requires careful consideration regarding the long-term preservation of artworks; for artists like Poidomani, the use of black light can enhance both the aesthetic and ideological depth of their works, adding new dimensions of meaning and engagement for the viewer.

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