In brief
Borax is a synonym for sodium tetraborate decahydrate. A 4% solution is suitable for use by year 7 students with suitable controls in place; these include wearing safety glasses and ensuring that hands are washed prior to leaving the laboratory. Gloves, such as latex or nitrile gloves, should be worn if the skin is broken. The solid chemical should be handled by staff using an operating fume cupboard to reduce the risk of inhaling dust. If you are using borax for making slime, you could consider safer alternatives such as slime made from cornflour or guar gum.
Additional information
Borax in solid form is a hazardous chemical which is classified as Reproductive Toxicity Category 1B, has the GHS08 (Health hazard) pictogram and carries the hazard statement H360 May damage fertility or the unborn child.
Information from Safe Work Australia’s Hazardous Substances Information System (HSIS) provides the cut-off concentrations for hazard classification. The cut-off concentration is the concentration above which the hazard classification for the chemical applies. In the HSIS, borax has a cut-off concentration of 8.5%.
A 4% solution is below this cut-off concentration and no hazard statements apply, however good laboratory practice should still be observed.
The National Industrial Chemicals Notification and Assessment Scheme (NICNAS) carried out an extensive assessment of borax considering domestic and industrial uses. Their advice for industry was that control measures should be implemented to minimise risks from exposure.
The reactivity of the borax as incorporated into the slime structure should also be considered. The NICNAS assessment advises that “dermal absorption of simple inorganic borates through intact skin is insignificant”. In slime, the boron is incorporated into the crosslinks of the polymer, which is likely to lessen the potential for it to be absorbed through the skin compared with simple inorganic borates.
In a school situation, solutions of borax less than 8.5% are appropriate for use by students. Science ASSIST recommends that solutions are prepared in an operating fume cupboard by staff and that the slime produced is washed with water before handling, to remove any unreacted borax. We suggest that pregnant women who are concerned about preparing a solution of borax discuss this with their employer and ask another trained person to prepare the solution.
We have answered related questions that have additional information:
References
‘Disodium tetraborate decahydrate [Borax decahydrate]’, Hazardous Substances Information System (HSIS, Safe Work Australia website, http://hsis.safeworkaustralia.gov.au/HazardousSubstance/Details?hazardousSubstanceID=5866 (20 March 2009)
'Disodium tetraborate, decahydrate' Safety Data Sheet. Please search the product information page of the Chem-supply website for the latest version: https://www.chemsupply.com.au (February 2020)
‘Human health tier II assessment for Borax (Na2(B4o7).10H2O)’, Inventory multi-tiered assessment and prioritisation (IMAP), Australian Government Department of Health, National Industrial Chemicals Notification and Assessment Scheme website, https://www.nicnas.gov.au/chemical-information/imap-assessments/imap-assessment-details?assessment_id=1328#cas-A_1303-96-4 (Accessed June 2016)
‘Investigating cross-linking – making slime’, Royal Society of Chemistry website, https://edu.rsc.org/resources/ (Accessed June 2016)
‘List of recommended chemicals for science in Australian schools’, Science ASSIST website, https://assist.asta.edu.au/resource/3052/list-recommended-chemicals-science-australian-schools?search-id=3d5a734 (18 March 2016)
Rohrig, Brian. 2014, ‘The Science of Slime’, pp13–16 in ChemMatters December 2014, American Chemical Society website, https://www.acs.org/content/dam/acsorg/education/resources/highschool/chemmatters/articlesbytopic/solidsliquidsgases/chemmatters-dec2004-slime.pdf
‘Time for slime’, American Chemical Society website, https://www.acs.org/education/whatischemistry/adventures-in-chemistry/experiments/slime.html (Accessed June 2016)