Technical note 15
TN-15: Colors and Finishes, the Red and Blue Palette
Working color and finish specification for a production version of the chair in the style of Rietveld's Red and Blue. Archived 24 August 2026. Status: ARCHIVED RESEARCH. This note preserves a research memo KU commissioned from ChatGPT; the raw text is in the project record (chair-book/notes/rb-colors-finishes-chatgpt-24Aug2026.md). Nothing here has been independently verified by this project: the construction facts are SOURCED by the memo to Cassina's published technical sheet, the historical account is SOURCED to the Rietveld Foundation, MoMA, and the cited workshop documents, and every color value is an ESTIMATE, read off photographs, not a factory formula. The one decision the note supports today is which swatches to order.
The practical spec: the current Cassina 635
Cassina, the licensed producer, publishes no Pantone, RAL, RGB, or HEX values; its technical sheet gives color names and finishes only. The memo's best visual estimates from Cassina's current imagery:
| Part | Estimated hex | Pantone approx. | Practical paint match |
|---|---|---|---|
| Black frame | #171717 | Black C | RAL 9005 Jet Black |
| Yellow ends | #F1C400 | 116 C | RAL 1023 Traffic Yellow |
| Red back | #D62B1F | 485 C | RAL 3020 Traffic Red |
| Blue seat | #124A8F | 2945 C | RAL 5005 Signal Blue |
Reasonable photographic ranges: red #C9231B to #E23A2C; blue #073E7A to #1B5DA5; yellow #E4B400 to #FFD21A; black #0B0C0D to #2A2A2A. The blue is the least certain: older examples read more violet, toward ultramarine, for which Pantone 2738 C or RAL 5002 would be the better choice than 2945/5005.
Specification doctrine, per the memo and endorsed here: specify RAL rather than Pantone for furniture coatings (Pantone describes ink on paper; RAL is built for coatings), then approve physical spray-outs before committing. Sheen is part of the color: Cassina runs semi-gloss ("half-polished") red and blue panels against a matte-black frame, and that sheen split substantially changes perceived color.
Rietveld's historical colors
There was no black-red-blue-yellow "original 1918" chair. The first example was unpainted, stained beech; the familiar primary treatment emerged around 1923, with the precise date uncertain, and Rietveld made numerous monochrome and client-specific versions. The best historically grounded specification is in color names, not codes: an undated Rietveld working drawing reportedly calls for black-stained framing, chrome-yellow ends, a vermilion-red back, and an ultramarine-blue seat, and a Van de Groenekan workshop example uses the same terms. Modern hue proxies for that palette:
| Historical description | Hex proxy | Pantone proxy | RAL proxy |
|---|---|---|---|
| Dark brown-black stain | #171411 | n/a | custom near-black stain |
| Chrome yellow | #FFA700 | 137 C | RAL 1007 |
| Vermilion red | #E34234 | 179 C | RAL 2002 |
| Ultramarine blue | #120A8F | 2738 C | RAL 5002 |
Two cautions travel with that table. Historians state plainly that no universal correct color numbers exist; Rietveld had colors individually mixed, so these are hue proxies, not recovered formulations. And the literal historical pigments, vermilion and chrome yellow, can contain mercury and lead; a production chair color-matches their appearance in modern safe pigments and does not reproduce their chemistry.
Cassina's construction, for reference
Per the memo's reading of Cassina's technical sheet: seat and back are birch multi-ply plywood cores faced and edged in beech veneer, finished in semi-gloss polyester lacquer; the frame is solid beech in matte-black lacquer with yellow crossbar ends; assembly is wooden joints with dowels and pins. Plywood, not MDF. Early Rietveld-built chairs varied, some with solid-board panels and documented later workshop examples in birch plywood, so Cassina's construction should not be projected backward onto every 1920s chair.
Open items
- Order RAL spray-out swatches in both palettes: the Cassina-modern set (9005 / 1023 / 3020 / 5005) and the historical set (near-black stain / 1007 / 2002 / 5002), each in the matte-frame and semi-gloss-panel sheens.
- Decide the blue: signal (5005) versus ultramarine (5002). This is the palette's largest visible fork.
- Verify the two Rietveld workshop documents the memo cites before any of this reaches print.
- Reconcile any chosen finish with TN-5's doctrine: thin and renewable beats thick film, and a lacquered production chair departs from that doctrine knowingly.
Sources, as cited by the memo
Cassina 635 product imagery and technical sheet (cassina.com); Rietveld Foundation, "De kleuren van de rood-blauwe stoel"; MoMA collection record 4044; the Rietveld construction workbook scan (archive.org, 1345_001); the Van den Bruinhorst documented workshop chair; Ida van Zijl on Rietveld's colors (rietveldhuizen-vve.nl). Links preserved in the archived memo. None fetched or verified in this session.
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