Testex Press-O-Film replica tape is available in a variety of thicknesses to facilitate profile measurement in differing ranges.
The primary range for measurement with replica tape is 0.8 to 4.5 mils (20 to 115 um). Use of Coarse Minus grade (<0.8 mil or <20 um) or X-Coarse Plus grade tape (>4.5 mil or >115 um) should be restricted primarily to checking measurements at the lower and upper ends of the primary range.
|Grade (descriptive)|| Range When Used With Gage
(mils) / (um)
|Fine / Medium||not applicable|
|Coarse Minus||0.5 to 1.0 / 12 to 25|
|Coarse||0.8 to 2.5 / 20 to 64|
|X-Coarse||1.5 to 4.5 / 38 to 115|
|X-Coarse Plus||4.6 to 5.0 / 116 to 127|
Further information (pdf format) on X-Coarse Plus grade tape is available here.
Testex replica tape can be used with a gage to measure the surface roughness ("profile") of blast-cleaned steel in the roughness range 0.8 to 4.5 mils (or 20 to 115 micrometers). Because inspectors, as a rule, have a target profile in mind. it is always best to start measurements with the grade of tape that has the target profile closest to the center of it's range.
Our Instructions webpage details the averaging procedure used in the overlap region between Coarse and X-Coarse grades.
Testex' lowest grade (thinnest) tape, Coarse Minus, should be used only to check measurements at the lower end of the next higher grade, Coarse, while our highest grade tape, X-Coarse Plus, should only be used to check measurements at the high end of the X-Coarse grade range.
Firmly compress tape with the smoothest surface on the rubbing tool provided, applying sufficient pressure to produce a replica with a uniform pebblegrain appearance. You should feel the roughness as you burnish.
Fine/Medium grade material is commonly used in applications in which the replica is analyzed using precision laboratory techniques. This grade is not suitable for use with a "dial thickness gage. Fine grade tape (rarely used) has a thin Gold coating to facilitate electron microscopy. Medium grade tape has a thin Indium coating to facilitate optical interferometric measurement. Fine and Medium grades have the same foam thickness. Only the vapor-deposited metallic coatings differ. "Unmetallized" Medium grade tape is also available without any metallic coating.
All grades are coated onto a tough polyester substrate 2.0 mils (50 um) in thickness.
Because implicit definitions of "roughness" vary between methods, numerical profiles determined using different techniques (replica tape, interferometer, confocal microscope, analog stylus, digital stylus) may yield different values. Always specify the technique used.