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Rosin
Table of contents
Key Data
Composition: Approximately 90% di-terpene acids (mostly from the abietic, also pimaric and labdanic groups), with the remainder being a mix of esters, alcohols, aldehydes and hydrocarbons.
CAS: 8050-09-7 - though note that there are a number of very similar variations with their own CAS numbers
Other names: colophony, Greek pitch, pine resin, wood rosin (extracted from roots), gum rosin (extracted by tapping trees) or tall oil rosin (extracted from paper making)
Appearance: A dark amber to clear translucent solid
Solubility: Almost insoluble in water (0.9mg/litre), but does absorb water. Soluble in many organic solvents so long as they are free of water.
Oxidation: At around 80-100*C rosin absorbs oxygen from the air and an exothermic reaction occurs, giving out significant amounts of heat and melting the rosin. As the reaction depends on oxygen diffusing from the air into the solid rosin, it is quite slow.
Melting Point: It melts over a temperature range, rather than a single temperature. Softening point is around 45-82*C. Half melted temperature is typically 90-175*C.
Flash point: About 180°C
Auto-ignition point: >400°C
Flammability: Burns with a yellow, sooty flame. On burning or thermal decomposition produces acetone, methanol, aliphatic aldehydes, carbon dioxide, carbon monoxide, methane, ethane, abietic acid, and related di-terpene acids;
Composition/Impurities
A product from pine trees, it may be produced from tree stumps (the purest source), or tapping pine trees, or as a by-product of turning trees into paper (the least pure form). The tree sap is turned into rosin and spirit of turpentine by distillation. It may then be treated to make it more suited to specific applications.
When sold as a powder, it may contain 10-20% (by weight) of magnesium or calcium carbonate as an anti-caking agent - see the supplier's specifications.
A synthetic rosin is also available, which is a chlorinated paraffin wax. It's chemistry is very different, so is probably not a suitable substitute, and is also a carcinogen.
Uses
Used as the reducing agent in resin lustres, especially those made by potters as opposed to commercially produced ones.
Rosin based adhesives are usually a blend or mixture of rosin, linseed oil, beeswax. Rosin based adhesives are sometimes used for restoration of ceramics in museums. The ratio of the ingredients vary in different recipes. You can modify the ratio of ingredients to obtain the texture, viscosity, tackiness and drying time that is best for your application.
A similar formula is used to produce ceramic printing inks. Linseed oil, other vegetable oils, rosin and pigment are the main ingredients of ceramic inks.
Exposure Routes
Skin and Eye Exposure
Slight sensitising effect on skin. Some sources say it is an irritant but this is probably for related chemicals rather than rosin.
Skin Absorption
Not absorbed through undamaged skin
Inhalation
Probably absorbed to some extent through the lungs
Ingestion
Probably absorbed to some extent
Toxicity
Acute
Skin
In allergic contact dermatitis, the dermatitis tends to occur 1-3 days after contact, although occasionally reactions can appear within 24 hours or even more than a week after exposure. The dermatitis tends to be confined to the site of contact, although the face may also be involved. Initially the skin becomes red and inflamed, and is generally itchy. As the reaction progresses it may blister and become even more intensely itchy. If exposure is continued, the dermatitis may eventually become chronic with thickened, lichenified skin.
Otherwise, no adverse effect at 2g/kg body weight (rat)
Inhalation
High exposure may cause temporary irritation to the respiratory tract. May cause asthma in sensitised people.
No evidence for other adverse effects.
Ingestion
High doses may cause gastrointestinal irritation with nausea, vomiting and diarrhoea. No adverse effect at 2g/kg body weight (rat)
Repeat Dose
Skin
Long term contact with rosin may cause contact dermatitis (see above).
Inhalation
Long term inhalation of the fumes of heated rosin may cause occupational asthma (colophony disease). If this occurs, no further contact with rosin should be permitted.
Ingestion
No information, but approved as a food additive.
Genotoxicity
No information available
Carcinogenicity
Not reported as a carcinogen
Reproductive Toxicity
No information available
Fire Hazard
The heat output from the oxidation reaction may be enough to set fire to rags, particularly if the rags are scrunched up. Place any used material into a lidded metal container and cover with water to prevent oxygenation. To reuse the rags, wash out and then dry on a washing line or laid out on a non-flammable surface, so heat cannot build up. To dispose of the rags, dispose of the sealed container, or place the wet rag into a Ziploc type bag and squeeze out the air before sealing. Depending on your location, the rags in bags may be able to be disposed of in household waste, or otherwise they may be classified as hazardous waste.
In the event of a fire, some sources say that a water based fire extinguisher may not be effective.
Health and Safety Practice
Keep in a closed container to avoid moisture absorption.
Keep away from acids and strong oxidising agents.
When handling powdered rosin extensively, it is recommended to wear gloves, safety glasses and a dust respirator. The risk of harm from occasional contact is minimal. However if a person has an allergy to rosin, then precautions must be taken to prevent skin contact.
When heating or burning rosin, e.g. in preparing lustres or firing in a kiln, protect against fumes through adequate ventilation (e.g. a kiln vent or local ventilation ducted outside) and/or by using a respirator with a suitable filter, e.g. brown A type in Europe, or black or yellow type in the USA.
Disposal
Toxic to aquatic organisms. Do not dispose of in waterways or drains or soil. Persistence in soil is unlikely.
Regulatory Requirements
Dust Limits
For unheated rosin, the limits are the same as for dust.
For heated rosin, the following are for rosin used as a flux in soldering, which will be similar to heating rosin when preparing a lustre, or firing a rosin based lustre in the kiln.
| _Regulator_ | _8 hr TWA mg/m³_ | _15 min TWA mg/m³_ |
| US NIOSH | 0.1 | |
| UK HSE | 0.05 | 0.15 |