What makes silk different from every other fibre
Silk is a protein fibre, like wool — but where wool is a spun staple fibre made of overlapping short fibres, silk is a single continuous filament spun by the Bombyx mori silkworm. A single silk thread from a cocoon can be hundreds of metres long. That continuity is what gives silk its strength-to-weight ratio and its characteristic sheen. It is also what makes silk more vulnerable to chemical and mechanical damage than any other common textile fibre.
How silk’s sheen works — and how cleaning destroys it
Silk’s lustre comes from the triangular cross-section of the individual filament. The three flat faces of the triangle each reflect light at different angles, producing the prismatic glow unique to silk. That cross-section depends on the structural integrity of the protein. Silk is held together by sericin, a natural gum the silkworm secretes alongside the fibroin that forms the thread. Alkaline chemistry dissolves sericin — permanently. Once sericin is gone, the characteristic sheen is gone with it, and the rug looks dull even when clean.
Heat does similar damage by a different mechanism: the fibroin protein structure begins to denature above roughly 100°F (38°C) under moisture. Hot-water extraction on a silk rug is catastrophic — not slowly over time, but in a single cleaning cycle.
Qum silk — the benchmark for fine silk weaving
Iranian Qum (or Qom) silk rugs represent the most refined silk weaving produced anywhere. Knot counts above 500 KPSI (knots per square inch) are common; truly exceptional pieces exceed 700. The higher the knot density, the finer each individual pile tuft — and the smaller the margin for any cleaning error. Qum silk is what informs the standards we apply to every silk rug. The same level of care we would give a museum-grade Qum applies to every silk piece that enters the workshop.
Dye sensitivity in silk
Silk takes dye more intensely than wool, which means dye instability problems are also more severe. Even slightly warm water can cause dye migration in fugitive silk dyes — the reds, oranges, and early synthetic purples that cause problems on wool rugs cause more dramatic problems on silk. Every silk rug we clean is dye-tested across every distinct colour field before any water touches the pile. The same discipline we apply to Persian wool rugs, but with narrower tolerances.
For the broader context on how we handle dye testing across all rug types, see our Persian rug cleaning guide.
What proper silk cleaning involves
Room-temperature or slightly cool water — never warm. pH-neutral or very mildly acidic solutions, around six to seven, with extensive dilution. Minimal mechanical agitation; the rug is worked by hand, gently, in small sections. Drying is immediate and controlled — silk cannot sit wet. The full conservation cleaning workflow is described on our rug cleaning service page; silk cleaning follows the same framework with tighter parameters at every stage.
Why silk rugs cost more to clean
Three reasons: time, chemistry, and risk. Silk cleaning takes three to four times longer per square foot than wool cleaning because every step is slowed down and monitored. The chemistry is more specific and uses more dilute solutions. And the underlying risk is simply higher — a silk rug we damage cannot be fixed. For silk pieces where cleaning has been delayed and structural issues have developed, conservation restoration may be appropriate rather than cleaning alone. We assess every silk rug on intake before quoting a process.