Arcare Neutral pH Adhesive – Independently Tested

Arcare neutral pH adhesive has been independently tested to ensure it meets the standards conservation professionals require.

Four other PVA adhesives, considered conservation standard by their manufacturer/retailer, were used in testing for comparative purposes. Tests were performed to determine the following; pH, Opacity, Off-gassing (Oddy test). A summary of the test and its results are detailed below:

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pH

Arcare pH adhesive was tested to show a pH of 5.9 (with an accuracy of +/- 0.05 pH). The other adhesives tested ranged from 5.8 – 6.2. All of the adhesives tested were considered safe for use with organic materials.

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Colour and Opacity

The range of adhesives were tested for their colour and opacity using a chromaticity meter. Cast at a thickness of around 1.5mm and dried to create a sample thick enough to register a reading (it’s accepted that this is much thicker than when actually used in conservation).

The image below recreates the difference in values provided by the test results using the L* a* b* values recorded (including the corrected background value).

Arcare PVA, although displaying an average colour change value of Eab 17.56 against a white background, was also one of the least opaque when measured against a black background. Combining the two figures gives an overall performance figure.

Adhesive	Against a white background	Against a black background	Total
PVA 1	14.62	25.48	40.1
PVA 2	13.24	31.21	44.45
Arcare	17.56	20.16	37.72
PVA 3	13.95	19.82	33.77
PVA 4	20.56	21.44	42

 

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Oddy Test

The Oddy test is a qualitative test for off-gassing, performed by observing corrosion in three metallic tokens (silver, lead & copper) sealed in an oven over 28 days at 60°C. Each metal detects corrosion in a different set of corrosive agents and a ‘Pass’, ‘Temporary use’, or ‘Fail’ grade is applied according to the level of corrosion perceived.

Adhesive	Silver	Lead	Copper
PVA 1	P	T	T
PVA 2	P	F	F
Arcare	P	T	T
PVA 3	P	T	F
PVA 4	P	T	T

(P) Pass / (T) Temporary Use / (F) Fail

Of the five adhesives tested, Arcare pH neutral PVA adhesive was one of three which did not fail any of the tests.

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Other Observations

Other qualitative observations made during the tests showed that, once dried, PVA 1 became brittle and shattered when cut with scissors. PVA 3 remained very flexible and was tackier than the other PVA samples after the Oddy test had been performed.

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The results of the tests show that Arcare PVA is a consistently high quality adhesive which can be relied upon in a variety of applications.

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Testing performed by Bainbridge Conservation – January 2016.