Paint a soap bubble in Aquarell: suggest a thin film with lost edges and local colour

A bubble can easily become a solid rainbow marble. Paint one large and one small bubble on a simple grey background, concentrating muted colour near selected edges and preserving much of the centre. This is a hand-painted thin-film study, not a physical interference simulation.

Establish sizes and spacing

On an approximately 1500×1500 px square, place a larger bubble left and smaller one upper right with a clear gap. Use a quiet grey background and faint circular guides. Separate colour edges and reflections, establishing stable circles and size hierarchy without thick black outlines.

Keep background in the centre

Preserve the background through most of the centre, changing colour and value mainly near selected edges. Avoid a uniform pale fill or erased background. Test one faint edge and one omitted edge, strengthening a local cue when needed instead of thickening the entire circumference.

Keep colour local along the edge

Use two or three muted violet, cyan or yellow arcs with varied width, not seven equally bright colours around a ring. Follow the sphere’s curvature and preserve gaps. Reduce length and intensity for a rainbow-tyre appearance, or align blotchy colours with the circular surface.

Suggest the environment through restrained reflections

Add a curved pale window-like reflection compressed by the sphere, with varied edge clarity. Avoid an unwarped white rectangle. Give the small bubble a related tiny accent. Keep reflection area concentrated and distinct from the colour arcs so the bubble does not become a bright disc.

Break the dark edges as well

Use a few slightly darker arcs on pale background without surrounding the bubble in complete black and white rings. Compare strongest and weakest edges within one circle. Reduce central shading and full outlines for a metallic or sticker-like result, allowing selected edges to disappear.

Repeat the rule rather than every detail

Give the small bubble fewer, finer colour cues under the same reflected light rather than scaling every large-bubble detail. Quiet it if it becomes brighter than the main bubble. Avoid an invented contact shadow under a floating subject; use size and background relations for space.

Check transparency through value relationships

Compare bubble centre with background, then the small areas of strongest light and dark. Squinting is enough without a special greyscale tool. Review hierarchy small and colour normally, repairing accidental arc corners close up. Local cues, not uniform fading, must establish the film.

Test transmission with a background band

In a test copy, pass a broad pale background band through the bubble centre. Preserve its identity without claiming exact refraction. Restore edge colour and reflections gradually, reducing interior paint if transmission disappears. Remove the test band afterward if it adds unnecessary decoration.

Compare strongest and lost edges

Compare one strongest arc with a nearly lost arc and check whether they still imply one circle. Repair faulty curvature rather than completing every outline. Preserve circular identity while varying information strength, reducing repetitive coloured lines instead of fading the whole image.

Make a colour-free test version

Keep a neutral-edge test and finished PNG with separate colour and reflection layers. Next, change only background warmth and reassess edge contrast before colour. If the neutral version still reads as a bubble, preserve its useful reflection and lost edge before adding stronger colour.

Related tutorials and sources

Transparency and contours, Opacity control.

Checked on October 27, 2026 against the official Aquarell App Store listing and Apple’s public version lookup: current version 1.0.6, requiring iOS / iPadOS 15.0 or later. This exercise uses public brush, colour, layer and saving capabilities. Geometry, materials and motion cues are drawn manually; dimensions, palettes and simplified forms are suggestions. Check controls in your installed version. Keep the native project for editing and use PNG for previews. No step-by-step physical-device testing is claimed.