Glove selection

A glove is the last control in the hierarchy, not the first. HSE’s brief guide to COSHH lists seven control measures in order of priority — eliminate the substance; use a safer form of it, paste rather than powder; change the process to emit less; enclose it; extract at the source; keep as few people near it as possible; and only then provide personal protective equipment. Every “required PPE” line in this course is the seventh item on that list, and it is there because the first six have already been applied.

This page is the table every practical page cites instead of inventing its own advice. It contains one thing the course insists on and most glove pages omit: a list of the substances for which no permeation data could be found at all. A table of confident cells covering data that does not exist would be the most dangerous page in the course.

The three ways a glove fails

HSE’s glove-selection guidance defines them, and they are three different failures with three different signatures.

• Permeation is the chemical migrating through the intact glove at molecular level. Nothing is visible. Ansell’s own comparison is a sealed balloon: no holes, and the air gets out anyway.
• Penetration is bulk flow through a seam, a pinhole, a tear or an open cuff. This is the one you can find by looking, and the reason Kodak asks you to check gloves for pinholes, leaks and tears and to discard damaged ones.
• Degradation is damage to the glove material itself — hardened, softened, swollen or embrittled by contact. A degraded glove’s permeation resistance collapses, and HSE notes that permeation and degradation do not always correlate, so a glove can look fine and be finished.

A manufacturer’s chart quantifies the first and third of those with three numbers per glove-chemical pair.

Breakthrough time is the time from the start of the test to the first detection of the chemical on the inside of the specimen, measured to ASTM F739 with the sample clamped in a cell and totally immersed.

Permeation rate is how fast it comes through once it has started, and it is not implied by the breakthrough time. Ansell’s own analogy is two hoses: the narrow one starts flowing first, the wide one delivers far more in a few minutes. A short breakthrough time with a low rate can expose you to less than a long breakthrough time with a high one.

Degradation rating is a letter: E excellent, G good, F fair, P poor, NR not recommended, and DD for a material whose outer layer degrades and delaminates. Two letters in the guide mean the test was not run — L, inferred good-to-excellent because breakthrough exceeded 480 minutes, and I, inferred from tests on similar compounds. Where a cell below carries one of those, it is an inference by the manufacturer, not a measurement.

The published table

Every figure below is from one manufacturer’s eighth-edition guide, and every column is a specific glove, not a material in general:

Column	Material	Glove tested	Thickness
Nitrile	Unsupported nitrile	Sol-Vex 37-165	0.56 mm (22 mil)
Neoprene	Unsupported neoprene	29-865	0.46 mm (18 mil)
Natural rubber	Natural rubber latex	Canners 343	0.51 mm (20 mil)
Blend	Neoprene and natural rubber latex blend	Chemi-Pro 224	0.68 mm (27 mil)
Butyl	Unsupported butyl	ChemTek 38-320	0.51 mm (20 mil)
PVC	Supported polyvinyl chloride	Snorkel	not stated in the guide

Breakthrough times are in minutes; the letter before each is the degradation rating for that pair.

Substance, as tested	Nitrile	Neoprene	PVC	Natural rubber	Blend	Butyl
Acetic acid, glacial 99.7 %	G 158	E 390	F 45	E 110	E 263	E >480
Sodium hydroxide, 50 %	E >360	E >480	G >480	E >360	E >360	E >480
Potassium hydroxide, 50 %	E >360	E >480	E >360	E >360	E >360	not tested
Sulfuric acid, 47 %	E >360	E >360	G >360	E >360	E >360	not tested
Sulfuric acid, 95–98 %	NR	F 24	G 26	NR	NR	E >480
Nitric acid, 10 %	E >360	E >480	G >360	G >360	E >360	not tested
Nitric acid, 70 %	NR	L >480	F 109	NR	NR	not tested
Hydrochloric acid, 10 %	E >360	E >480	E >360	E >360	E >360	not tested
Hydrochloric acid, 37 %	E >480	E >480	E 300	E 290	E >360	not tested
Oxalic acid, saturated solution	E >360	E >480	E >360	E >360	E >360	not tested
Citric acid, 10 %	E >360	E >480	E >360	E >360	E >480	not tested
Hydroquinone, saturated solution	E >360	E 108	E >360	G >360	E >360	not tested
Ammonium hydroxide, 28–30 %	E >360	E 250	E 240	E 90	E 247	E >480
Ethanol, denatured 92 %	E 240	E 113	G 60	E 15	E 37	E >480
Isopropyl alcohol	E >360	E 110	G 150	E 35	E 57	not tested
Hydrogen peroxide, 30 %	E >360	E >480	E >360	E >360	G >360	not tested
Formaldehyde, 37 % in methanol and water	E >360	E 39	E 100	E 10	E 32	E >480
Glutaraldehyde, 25 %	E >360	E >480	E >360	E 210	not tested	not tested
“Chromic acid” cleaning solution	F 240	NR	G >360	NR	NR	E >480
Diethyl ether	E 95	F, under 10	NR	NR	NR	not tested
Benzene	P, no time	NR	NR	NR	NR	E 20
Mercury	L >480	not tested	L >480	L >480	not tested	not tested

NR is the guide’s not recommended; a cell reading “not tested” means the guide carries no figure for that pair, which is not the same as a poor result.

Four things in that table are worth stopping on.

Materials do not rank; pairs rank. Neoprene beats nitrile on most of the aqueous rows and then falls to 108 minutes on saturated hydroquinone, 39 on formalin and under 10 on diethyl ether, where nitrile gives 95. There is no column that wins.

Natural rubber collapses on the alcohols and on formalin — 15 minutes for ethanol, 35 for isopropanol, 10 for formaldehyde solution — while holding for hours against the aqueous acids and alkalis. Thickness does not explain it: the 0.68 mm blend behaves the same way. Solvent and polymer either get on or they do not.

The concentrated mineral acids break the darkroom default. Nitrile is not recommended against both 95–98 per cent sulfuric and 70 per cent nitric, and so are natural rubber and the blend; butyl holds for more than 480 minutes against the sulfuric acid and is untested against the nitric, and neoprene’s “>480” for nitric is one of the guide’s L inferences rather than a measurement. This course handles neither acid at those strengths. The rows are here so that a reader who meets one elsewhere does not assume the darkroom’s default glove carries over.

A ninth column exists that the course never recommends. Supported polyvinyl alcohol is not recommended against nearly every aqueous entry in the guide while performing well against benzene and ether. It is a solvent glove, and the darkroom’s chemistry is aqueous. Household washing-up gloves are a different point again: Kodak states plainly that gloves sold for household use may not be durable enough for photographic processing chemicals.

✕Four reasons this table does not answer the question you are asking

1. The thickness is wrong for a darkroom. 0.56 mm is a heavy reusable industrial glove. HSE’s control sheet for manual film development takes single-use nitrile 0.2 mm thick as typically acceptable splash protection where the safety data sheet gives no specific advice, and new 0.4 mm nitrile for cleaning up a spill. A thinner glove breaks through sooner: the figures above are an upper bound on a glove you have not bought.
2. The test is total immersion. A drop wiped off in five seconds is a different exposure. HSE’s own selection form asks whether the worst-case contact is dipped, splashed or touch.
3. The data are for pure chemicals, and you never handle one. HSE states it directly: manufacturers’ data are measured on pure chemicals rather than mixtures, and mixing changes the properties. The rule of thumb is to select on whichever component has the shortest breakthrough time. Your developer is eight substances in water.
4. The manufacturer says so itself. The guide’s introduction states in capitals that the suitability of a product for a specific job must be determined by testing by the purchaser, and that the recommendations are advisory.

What the course could not source

This section is the reason the page exists. For the following substances — several of them the ones a reader of this course handles most — the permeation guide this course read contains no entry at all, and no other tier 1 or tier 2 permeation figure has been found for them.

Substance	Where the course uses it	Status
Silver nitrate, solid and in solution	Parts I, IV, V and every printing-out process	No entry in the guide. This course looked and it is not there
Sodium thiosulfate, ammonium thiosulfate	Every fixer, from Part I onward	No entry
Metol, phenidone, p-aminophenol, glycin	Every developer	No entry
Hydroquinone in an alkaline developer	Every developer	The guide’s entry is a saturated aqueous solution, which is a different liquid from a carbonate-buffered developer
Sodium sulfite, sodium carbonate, potassium bromide	Every developer	No entry
Potassium ferricyanide, potassium ferrocyanide	Reducers, toners, cyanotype	No entry
Chrome alum, potassium alum	Emulsion hardening, hardening fixers	No entry
Selenium toner, sodium selenite, gold(III) chloride	Toning	No entry
Ferric oxalate, ammonium iron(III) citrate	Iron and iron-silver processes	No entry
Erythrosin	Part V, project 5	No entry
Gelatin, at 50 °C	All of Part V	Not a permeation question; the hazard is thermal

What follows from an absent figure. Not that the substance permeates freely, and not that it does not. It means there is no number, so the control cannot be a contact time you looked up. What the course does instead, and what every affected page says in its own Required PPE section:

What replaces a breakthrough time when there is no breakthrough time

1. 11. Treat the glove as splash protection, not as a barrier with a clockHSE names single-use nitrile of about 0.2 mm as typically acceptable splash protection where the safety data sheet gives nothing more specific. That is the basis this course uses for silver nitrate.
2. 22. Make the permitted contact time short and explicitA splash is wiped or rinsed off at once and the glove is changed. The page says so rather than quoting a figure that does not exist.
3. 33. Change the glove on any contamination, not on a scheduleContamination you can see is the trigger. With silver nitrate the stain arrives later than the contact, so a mark on a glove means the change is already overdue.
4. 44. Keep the substance off the glove in the first placeTongs, a funnel, a tray, a syringe for a stock solution. The six controls above PPE in the hierarchy do more than the glove does.
5. 55. Say on the page that the figure is missingA reader who is told there is no permeation figure can make their own decision. A reader given a plausible number cannot.

This is the course's standing practice where permeation data do not exist, and it is what the silver nitrate pages already do.

What the course uses, and on whose authority

Situation	Glove	Source
Routine handling of working-strength solutions	Single-use nitrile, about 0.2 mm	HSE COSHH essentials sheet P1, as typically acceptable splash protection where the SDS gives no specific advice
Cleaning up a spill	New nitrile, 0.4 mm, with an impervious apron	HSE, same sheet
Photographic processing generally	Neoprene or nitrile	Kodak’s handling publication
Any handling or mixing of photochemistry	Suitable gloves, with eye or face protection	ILFORD’s health and safety guidance
Handling clean dry glass before coating	Cotton, and it is not chemical protection	The two jobs are different, and Part V’s plate pages say which is which

Cotton gloves keep skin oils off glass. They do nothing whatever about a liquid, and a page that lists them has to say so, or a reader will substitute one for the other.

Latex, and why the course avoids it

Not for chemical reasons: the natural-rubber column in the table above is respectable. HSE’s guidance is to choose non-latex gloves unless there is no alternative that gives the protection needed, and, where latex must be used, to use low-protein powder-free gloves. The hazard is natural rubber latex protein allergy — contact urticaria — which is an allergy acquired by wearing the glove, in a person who had none before. A control that creates a new sensitisation is a poor control, and HSE’s account of sensitisation is that once it is acquired, tiny amounts trigger a reaction and the only remedy is to prevent further exposure.

Four limits that apply to every glove in the table

No glove is tested to give more than eight hours of protection against chemical permeation, and no test includes wear, stretching or abrasion.

Gloves cannot be maintained. HSE’s control sheet is blunt: they are nearly always contaminated inside the second time they are put on, and permeation continues through the material while the glove sits in a drawer. A contaminated inner surface holds the chemical against skin for as long as the glove is worn, which HSE elsewhere describes as potentially greater exposure than wearing none at all.

Single-use means single use. They are discarded when they come off, which is why the removal sequence exists — rinse them while still worn, peel the first inside out, get a bare finger inside the second cuff, and let no bare skin touch an outer surface.

A glove is not the only thing your hands meet. A freshly cut sheet of glass will cut through a nitrile glove, which is a mechanical failure no permeation table describes. Part V’s plate pages handle that with edge treatment rather than with a thicker glove.

⚠The one-line version, for a page that needs to cite something

Nitrile single-use gloves of about 0.2 mm are this course’s default for working-strength solutions, on HSE’s authority, as splash protection with a short permitted contact time — not as a barrier with a published breakthrough time, because for most photographic chemicals no such figure exists. Where a page needs something else, it says which glove and why.