3M 616 Lithographers Tape is a red-transparent polyester-backed pressure-sensitive tape supplied for negative assembly, prepress masking, and photopolymer plate correction. The product combines a pigmented polyester backing with a rubber-based adhesive system. Dimensional values determined under ASTM D3652 identify a nominal total thickness of 0.028 mm (1.1 mil). Tensile property measurements under ASTM D3759 report a break strength of approximately 25 lb/in (4.4 N/mm) and an elongation at break near 100%. Peel adhesion to stainless steel tested according to ASTM D3330 is commonly reported near 6.4 N/25 mm. The red polyester film attenuates actinic UV and blue wavelengths while transmitting enough red light for visual alignment and inspection through the tape. It is supplied in roll format with slit widths matched to stripping table and step-and-repeat machine requirements. The backing thickness and modulus support clean manual tearing, minimal edge curl, and low mechanical stand-off in contact platemaking.

How Does 3M 616 Perform Under Vacuum-Frame Drawdown and Contact Exposure?

In a vacuum frame operating at drawdown pressures from 20 kPa to 95 kPa, the height of a taped film edge is a primary variable in halftone contact quality. A single layer of 3M 616 over a 0.100 mm polyester carrier creates a local step height of approximately 0.128 mm. That value exceeds the common process rule that the film-to-plate gap in contact exposure should remain below 0.05 mm for fine-line and stochastic plate work near 10 µm feature size. Consequently, tape placement at the edges of active image areas should be avoided or the taped assembly should be passed through a roller laminator after application to compress the adhesive and reduce trapped air. The polyester backing resists tensile creep during manual stripping, which preserves registration over large imposition flats. Unlike creped paper tapes, the material does not absorb moisture during high-humidity room conditions, so dimensional stability is maintained at relative humidity levels up to 60%. Published manufacturer data for drawdown-specific imaging tests are limited; confirmation is required where screen rulings exceed 150 lpi.

Roll handling on stripping tables requires a tape with consistent unwind force. The polyester backing of 3M 616 produces predictable unwind tension in manual dispensers and consistent feed in semi-automatic applicators. The product is slit from master rolls; edge quality is controlled to minimize adhesive peaks at the cut edge. In automated stripping tables, edge notching is relevant because it affects the registration of tape application. A clean, burr-free edge permits tape to be applied parallel to the film edge without skewing. No specific unwind force curve is published in accessible literature for 3M 616; converter or current supplier data should be consulted when specifying brake settings on motorized dispensers.

Thermal exposure in plate processing is governed by the tape’s maximum service temperature. 3M literature reports a short-term maximum service temperature of 149 °C (300 °F). Solvent-developed photopolymer plates are typically dried and post-exposure baked at 100 °C to 120 °C, which is inside the stated limit. Dwell times in conveyorized dryers of 30 s to 120 s do not normally induce backing shrinkage. The rubber-resin adhesive is softened by aromatic hydrocarbon and ketone fractions present in some plate developers. No universal compatibility threshold is published because developer recirculation rate, bath temperature, and immersion time vary. Alkaline washout chemistries with pH above 10.5 can reduce adhesive anchorage at the polyester interface under repeated bath immersion. For critical plate runs, validation should be performed with the actual processor chemistry and dwell time. Current REACH and RoHS certificates for the specific roll lot should be obtained where the tape is used in export-bound prepress workflows. The tape does not contain creped paper fibers, which eliminates a source of developer filter contamination in high-volume processors.

Solvent resistance should be assessed against the washout chemistry used in the plate processor. Rubber-based adhesives are generally resistant to aliphatic hydrocarbons and mild aqueous cleaners, but aromatics and ketones can soften the adhesive layer. In aqueous flexo platemaking, where plates are washout with warm water at 40 °C to 60 °C, the tape is normally outside the washout zone unless it is used to mask unused areas of the plate. If developer is sprayed at pressures above 2 bar, direct impingement on the tape edge can initiate lifting. Placement of the tape away from high-pressure spray nozzles is preferred. The polyester backing is not degraded by water or common alcohol-based plate cleaners, but sustained immersion in high-pH developer may cause edge wicking and milky adhesive appearance.

Surface preparation for high-tack adhesion is limited to dry, oil-free film surfaces. The lithographic film should be free of anti-static residues and bulk fingerprint oils before tape application. Applying the tape at room temperature between 18 °C and 25 °C permits the adhesive to wet the polyester carrier without excessive flow. At temperatures below 10 °C, tack is reduced and the polyester backing becomes stiffer; in cold prepress areas, rolls should be conditioned to ambient temperature for 24 h before use. At application temperatures above 40 °C, adhesive ooze at the edge increases over long dwell times. This operational window is consistent with pressure-sensitive tapes of the rubber-resin class and is not unique to 3M 616.

When Step-and-Repeat Imposition Requires Spectral Blocking With Minimal Edge Stand-Off

In step-and-repeat workflows, the tape is used to fix film positives to carrier sheets, mask pinholes in opaque areas, and block stray actinic light at the perimeter of cut film. The red pigmentation of the polyester backing functions as a short-wavelength filter while retaining red-light transmission for alignment. The tape is not a substitute for dedicated red masking film when edge straightness below 0.01 mm is mandatory, because hand-applied tape edges are not as geometrically exact as knife-cut machine mask edges. Where dot-for-dot register is required for stochastic rosette output, a UV densitometric check should be performed at the platesetter’s dominant exposure wavelength, typically 365 nm or 405 nm. Published spectral absorption curves for 3M 616 are limited in publicly available literature; users should request current manufacturer spectrophotometric data when the tape is placed near high-resolution image apertures. The product’s 0.028 mm thickness permits it to be used at the edge of frame openings without producing a mechanical slope that displaces film or plate contact. In multiple-burn imposition, the adhesive is removable from uncoated polyester carrier sheets after dwell times up to 72 h at 23 °C, minimizing carrier rework.

Adhesive Residue Transfer, Roller Tracking, and Punch-Stability Testing

Adhesive transfer from 3M 616 onto plate surfaces depends on dwell time, temperature, and substrate surface energy. On uncoated polyester carrier sheets, clean peel is generally observed after dwell durations up to 72 h at 23 °C. On photopolymer plate surfaces, residue risk increases when the tape is subjected to storage temperatures above 40 °C for extended periods. Punch and bender machines fitted with register pin systems impose localized shear on taped film edges. The polyester backing provides sufficient shear resistance to prevent adhesive phase separation at punch stations where side-lay sensors exert repeated lateral load. Because the total thickness of the tape is less than 0.03 mm, pin engagement on register bars with pin clearances larger than 0.1 mm is generally not impaired. Multiple tape layers should be avoided because the cumulative height can alter pin insertion depth and create a cantilever effect on polymer plates. The film does not contribute fiber debris to roller or punch tooling, which reduces cleaning frequency on automated benders. For solvent-free adhesion, 3M 616 can remain on the carrier during multiple-burn imposition without removal or solvent pre-cleaning when dwell conditions are controlled.

Compared with clear polyester splicing tapes, 3M 616 differs primarily in spectral response rather than mechanical gauge. Clear polyester tapes in the same thickness class do not block actinic wavelengths and are therefore limited to splicing, while 3M 616 can be used as a red mask repair tape. Compared with paper lithographic tape, 3M 616 eliminates paper fiber contamination and offers higher thermal resistance: paper crepe backings typically degrade above 100 °C, while the polyester backing is rated for continuous dry heat to 149 °C. Compared with red vinyl masking tape, 3M 616 provides lower elongation under tensile stress and lower residual surface contamination because it does not rely on phthalate plasticizers. However, the polyester backing is less conformable around tightly curved register pins. Table 1 summarizes these class-level differences.

Clear polyester and paper product data are vendor-dependent and are provided only as industrial class comparisons; they are not substitutes for supplier certification.

Why Thickness and Spectral Response Separate 616 From Vinyl Masking Tapes

The spectral response of 3M 616 is produced by pigment distributed through the polyester backing rather than by a surface ink or lacquer. This construction avoids the surface cracking and pigment flaking that can occur with red vinyl tapes. In red vinyl masking films, plasticizer migration can alter film flatness and transfer a low-viscosity residue to polyester carrier sheets; the polyester backing of 3M 616 is free of that plasticizer migration mode. The 0.028 mm gauge permits the tape to be used in butt-splicing of film positives where two film edges must remain nearly coplanar. Thicker vinyl tapes introduce a higher step edge that traps air in vacuum frames. The tensile strength of approximately 4.4 N/mm provides sufficient mechanical resistance for manual application and slitting without edge distortion, while the rubber adhesive supplies enough tack for uncoated polyester and matte film surfaces. Users replacing red vinyl tape with 3M 616 should note the lower elongation of polyester, which reduces compliance around curved surfaces but improves registration stability on flat imposition tables. Operational boundaries include storage below 40 °C and avoidance of aromatic solvents, especially where the tape is left in place during long-term negative storage. In prepress houses operating according to ISO 12647-2 conforming workflows, registration is tied to plate fit; dimensional and thermal stability of the masking material are relevant variables.