Perma Wash

Perma Wash is Heico's wash-aid product, used between fixing and the final wash to displace residual thiosulfate ("hypo") from the paper or film and dramatically reduce required wash time. Heico Chemical Company has manufactured Perma Wash since the 1960s; the product is sold as a liquid concentrate that dilutes 1:9 with water for normal print use (1:30 for film, per Heico's labeled instructions). Functionally equivalent to Kodak Hypo Clearing Agent (HCA) and Adox Adoflo II — same chemistry family, different brand and physical form.

Wash-aids are not optional for archival fiber-base prints. Without one, fiber prints require 60 minutes or more of running-water washing to bring residual thiosulfate below the ANSI/ISO archival threshold;^[1] with a wash-aid bath, the same paper reaches the threshold in 10–20 minutes of running water. RC paper and most films wash quickly without help, but a wash-aid step still measurably reduces residual silver-thiosulfate complexes that contribute to long-term staining.

When to choose Perma Wash over alternatives

• Prefer Perma Wash when: you want a liquid concentrate that handles conveniently (no powder weighing), Heico is locally available at reasonable cost, and you're working with prints (the 1:9 dilution is calibrated for print use).
• Prefer Hypo Clearing Agent (Kodak HCA) when: you already keep HCA powder on hand for other reasons, or you want the longer-shelf-life dry form. Functionally identical chemistry.
• Prefer Adox Adoflo II when: you're in Europe, where Adox is the easier supply chain.
• Prefer DIY 2% sodium sulfite when: you want to eliminate brand dependency or you're using a long-shelf-stock workflow. The active ingredient is just sodium sulfite at ~2% — though the commercial formulations include trace stabilizers and surfactants that the bare-chemistry version lacks.

How wash-aids work

The fixer dissolves unexposed silver halides as silver-thiosulfate complexes (mostly Ag(S₂O₃)₂³⁻). After fixing, the print or negative is saturated with these complexes plus free thiosulfate ion. Plain-water washing relies on diffusion to leach them out — a slow process for fiber-base paper because the gelatin layer holds onto thiosulfate ions strongly and the paper base absorbs solution into its fibres.

Wash-aids work by displacing thiosulfate ions with a more easily-rinsed sulfite ion. Sodium sulfite (Na₂SO₃) at ~2% concentration shifts the ion equilibrium so that thiosulfate diffuses out of the paper into the wash-aid bath in 2–3 minutes. The follow-up running-water wash then removes the sulfite (which rinses much faster than thiosulfate) along with any remaining thiosulfate. The net effect is the same archival endpoint reached in roughly a third of the time.^[2]

Perma Wash's commercial formulation is sodium-sulfite-based with proprietary surfactants and stabilizers — Heico has not publicly disclosed the exact composition, but published analyses suggest sodium sulfite plus a mild chelating agent.

Dilution and timing

Heico's labeled instructions plus widely-published archival workflow conventions:

Use case	Dilution	Working time	Final wash
Fiber-base prints (8×10 RC capacity rinse)	1:9 (1 part concentrate + 9 parts water)	2–3 min, 20°C, occasional agitation	15–20 min running water
RC prints	1:9	2 min	2 min running water
35mm / 120 film	1:30	1–2 min	5–10 min running water
Sheet film (4×5 and larger)	1:30	2–3 min	10 min running water

Capacity: roughly 30–50 8×10 prints per litre of working solution. Used solution that's gone cloudy or sulfurous-smelling has spent its sulfite reserve; discard and mix fresh.

Working-solution life: Heico's recommendation is to mix fresh per session and discard. Sealed working solution keeps 24–48 hours; unsealed solution oxidizes within a few hours.

Archival permanence rationale

Why this step matters for fiber prints intended to last:

• ANSI/ISO archival standard for B&W prints: residual thiosulfate ≤ 0.014 g/m² silver-thiosulfate complex, measured by methylene-blue test. Without a wash-aid, fiber prints typically reach this threshold only after 60+ min running-water washing; with a wash-aid, 15–20 min is sufficient.^[1]
• Failure mode without wash-aids: residual thiosulfate slowly reduces silver image to silver sulfide over years to decades, producing yellow-brown highlight stain and overall image fade. The chemistry is irreversible — once fading sets in, no re-treatment recovers the original print.
• Selenium-toning compatibility: Perma Wash working solution can serve as the carrier for Kodak Rapid Selenium Toner (mix selenium concentrate into Perma Wash working solution at 1:20 toner-to-wash-aid). The wash-aid keeps thiosulfate from interfering with selenium-silver reaction; the alternative — toning straight from a water rinse — gives less reliable colour.

For archival workflow, the proven sequence is: fix → first wash (1–2 min) → wash-aid (2–3 min) → optional toning → final wash (15–20 min) → optional Kodak HE-1 hypo eliminator (peroxide / ammonia) for museum-permanence requirements.

Comparison with alternatives

Product	Form	Active chemistry	Dilution (prints)	Notes
Heico Perma Wash	Liquid concentrate	Sodium sulfite + surfactants	1:9	US-common, convenient liquid form
Kodak HCA	Powder	Sodium sulfite + sodium bicarbonate	1:9 (from mixed working solution)	Discontinued by Kodak Alaris 2022; old stock still common
Adox Adoflo II	Liquid concentrate	Sodium sulfite + surfactant	1:9	EU-common alternative
Ilford Washaid	Liquid concentrate	Sodium sulfite + surfactant	1:9	UK-common alternative
DIY 2% sodium sulfite	Self-mixed	Sodium sulfite	Mix to 20 g/L	Cheapest; requires a powder-handling step but eliminates brand dependency

For darkroom workers running through a litre of wash-aid concentrate per year, the cost difference between brands is minimal; choose by local availability and personal preference.

Practical notes

• Choose Perma Wash over Kodak HCA based on availability and cost — the chemistry is functionally identical and either product will reach the archival endpoint.
• Liquid concentrate handles more conveniently than HCA powder for routine darkroom use; no weighing step.
• Concentrate keeps 1+ year sealed; opened concentrate keeps 6+ months in a tightly-capped bottle stored cool and dark.
• Working solution keeps 24–48 hours sealed; mix fresh for each session if possible.
• Selenium-toning carrier: working solution can be reused as the Kodak Rapid Selenium Toner carrier (KRST + Perma Wash works the same as KRST + HCA — the wash-aid sulfite buffers the toner against thiosulfate carry-in).
• PPE: nitrile gloves recommended; mild irritation potential from prolonged skin contact. The product is mildly alkaline and not strongly hazardous, but the same hygiene practices used for other darkroom chemistry apply.
• Don't pour exhausted wash-aid to drain with fixer: fixer disposal requires silver-recovery; wash-aid alone is drain-safe but never reuse a wash-aid tray for fixer or vice versa.

Related recipes

• Hypo Clearing Agent (HCA) — Kodak's functionally equivalent powder alternative.
• Kodak Fixer (F-5) — preceding fixer step for fiber prints.
• Rapid Fixer — preceding fixer step for RC prints and film.
• Kodak Rapid Selenium Toner — can use Perma Wash working solution as toner carrier.