New HYDAC Membrane Patch Colorimetry Kit for Varnish Potential Testing

Membrane patch colorimetry (MPC) for varnish potential testing (ASTM D7843) is an essential analytical test to determine the propensity for a lubricant to form varnish deposits.


MPC values increase as dissolved oil breakdown products, and (varnish precursors) accumulate. These breakdown products are produced by oxidation and begin to accumulate from the first moment that the lubricant goes into service.


Each lubricant has a finite capacity (saturation point) to hold these dissolved oxidation products in solution. Once this point is reached, the lubricant becomes saturated and excess breakdown products are forced from the fluid, forming harmful lubricant varnish deposits … i.e. can be in the form of particulate.


Once formed, lubricant varnish has a natural attraction for metal surfaces because of the polar nature of both the varnish and the metal. As varnish begins to coat metal surfaces, mechanical clearances are reduced, decreasing equipment performance and, ultimately, leading to failure.


With the probability of varnish-related failures reported to be as high as 100%, monthly MPC testing is recommended for all critical turbine, hydraulic and lubrication applications.


The ASTM-approved MPC test is straightforward and can be completed as part of your existing lubricant analysis testing program. It can also be performed on-site using a modified test method for rapid assessment of potential varnish-related problems.


The intensity and color of the patch is measured against a control patch using a spectrophotometer that calculates the color difference, or  ΔE value. The ΔE value and the corresponding propensity for the formation of lubricant varnish deposits are then assessed according to an MPC scale.

Typical MPC scale to determine lubricant potential for varnish formation 

ISADRAULICS are excited to announce the release of HYDAC INTERNATIONAL’s new MPC Patch Test kit. The kit includes a Spectrophotometer and allows you to do your own MPC tests without the need to pay for expensive laboratory results and mitigating the need to wait.


At HYDAC INTERNATIONAL, the Spectrophotometer is calibrated to ASTM D7843-12 (Standard Test Method for Measurement of Lubricant Generated Insoluble Color Bodies in In-Service Turbine Oils using Membrane Patch Colorimetry) and the kit provides the user with everything needed to check and control varnish.


The Spectrophotometer is a lightweight, portable, palm-sized photocell detector to measure MPC varnish potential. MPC varnish potential readings are obtained by using to scan 47 mm (0.45 μm) nitrocellulose patches, which have been prepared according to ASTM D7843-12.


Furthermore, in controlling, mitigating and managing varnish build up in your oil, ISADRAULICS offer a self-contained, rugged and portable Varnish Elimination unit by HYDAC INTERNATIONAL that is unique in ways that it can be applied to a working system with no requirement to stop or interfere with the operation, thus it is a real on-line and on-load varnish solution.


For further information on either the HYDAC INTERNATIONAL Patch Kit-MPC, or the VEU “Varnish Elimination Unit”, please call ISADRAULICS on +61 7 4743 9139, or e-mail [email protected] for further information.

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