Last updated: October 2026
Quick answer: CTcP (computer to conventional plate) images a positive-working UV-sensitive plate directly with UV light, so there is no film and no contact frame. The process is: RIP the job to a 1-bit TIFF, expose the plate in a UV platesetter, develop it in a plate processor, rinse, gum and dry it, then check it. Baking is optional for longer conventional-ink runs. Our CTcP plate can be baked but is not UV-ink resistant.
Key takeaways
- CTcP removes film and contact copying; the plate is imaged directly from a 1-bit TIFF.
- Our CTcP plate is positive-working: the exposed area is removed in the developer and becomes the non-image area.
- Most quality problems come from exposure energy and developer condition, not from the plate itself.
- Calibrate with a step wedge and dot target before you linearise the RIP.
- Baking extends conventional-ink runs; it does not make our CTcP plate suitable for UV inks.
Many printers move to CTcP to get rid of film while keeping plate cost lower than thermal. Some still believe CTcP quality is not as good as thermal. In our experience a calibrated CTcP line with a well-kept developer gives stable dots for most commercial, book and packaging work. When highlight dots disappear after development, or dot gain drifts from week to week, the cause is usually in the process rather than in the plate. This guide walks through the CTcP plate making process step by step, the parameters to control, and the faults we see most often. For the plate itself, see our CTcP plates page.
What is CTcP plate making?
CTcP stands for computer to conventional plate. A UV platesetter writes the image straight onto a UV-sensitive offset plate, using UV light, typically from laser diodes or a UV light engine around the 400–410 nm range. Before CTcP, the same type of plate was exposed through film in a vacuum contact frame. CTcP removes the film, the film processor and the dust and register problems that come with contact copying.
Compared with thermal CTP, which images heat-sensitive plates with an 830 nm infrared laser, CTcP plates are usually lower in cost and are handled under yellow safelight before development. Our comparison of thermal vs UV CTP plates covers that choice in detail.
| Item | Film + PS plate | CTcP | Thermal CTP |
|---|---|---|---|
| Imaging | Film exposed in a contact frame | UV light directly on the plate | 830 nm infrared laser on the plate |
| Film cost | Yes | No | No |
| Plate working type | Positive PS | Positive-working | Positive-working (processless: negative-working) |
| Handling before development | Yellow safelight | Yellow safelight | Room light within TDS limits |
| Developer | PS-type developer | Standard PS-type developer | Thermal plate developer |
The CTcP process step by step
- Prepress and RIP. The imposed PDF is processed in the RIP: it is interpreted, screened with AM or FM screening, corrected with the linearisation curve and written out as a high-resolution 1-bit TIFF for the platesetter. Our guide to the CTP RIP workflow explains this step. The RIP is normally included with our platesetters or offered as an option, confirmed in the quotation.
- Plate loading. Plates are loaded by hand or from an autoloader under yellow safelight. Remove slip sheets, keep the coating side clean, and do not touch the coating with bare hands.
- UV exposure. The UV platesetter exposes the plate according to the 1-bit TIFF. Our CTcP plate is positive-working: the exposed coating becomes soluble in the developer, while the unexposed coating stays on the plate.
- Development. In the plate processor, alkaline developer dissolves the exposed coating and opens the hydrophilic grained aluminium, which becomes the non-image area. The unexposed coating remains as the ink-receptive image area.
- Rinse. Water rinses off the remaining developer so it does not carry over into the gum section.
- Gumming and drying. A thin, even layer of plate gum protects the non-image area from oxidation and fingerprints, which otherwise cause toning on press. The plate is then dried with warm air.
- Inspection. Check the control strip, highlight and shadow dots, register marks and background before the plate goes to press or to the oven.
- Baking (optional). For longer runs with conventional inks, apply baking gum and bake the plate in a baking oven at the temperature and dwell time in the grade TDS, then wash off and re-gum. See our printing plate baking guide. Baking does not make our CTcP plate UV-ink resistant; for UV inks use a double-layer thermal plate or trial a processless plate.
Key process parameters to control
A stable CTcP line comes down to four controls. Set them from the grade TDS, then keep them stable and record them.
| Stage | What to control | Typical reference | If it drifts |
|---|---|---|---|
| Exposure | Exposure energy and focus | Our current CTcP TDS: around 50–80 mJ/cm² in the UV range | Too high: highlight dots shrink or disappear. Too low: the background does not clear and tones. |
| Developer | Temperature, conductivity, replenishment | Standard PS-type developer at about 23 ± 2 °C | Too hot or too strong: fine dots are attacked. Too cool or tired: incomplete development and toning. |
| Development time | Processor speed (dwell time in developer) | Set per the grade TDS and processor | Too short: under-development. Too long: image area is attacked. |
| Dot reproduction | Linearisation curve | Our current CTcP TDS: 2–98% at 200 lpi | Dot gain moves when the curve is not re-checked after a process change. |
When you first switch to our plate, run a short calibration: image a step wedge and a dot-gain target, check the 2% and 98% patches after development, and adjust exposure energy before you linearise the RIP. Some operators believe a stronger developer cleans the plate better; in practice it eats highlight dots. Keep the developer at the TDS condition and let replenishment do its job.
Common CTcP faults and how to fix them
| Symptom | Likely cause | What to check |
|---|---|---|
| Background tones on press | Exposure energy too low; developer tired, cool or under-replenished; gum missing or thin | Step wedge reading; developer temperature and conductivity; gum coverage |
| Highlight dots disappear after development | Exposure energy too high; developer too hot or too strong; dwell too long | Exposure against the TDS; developer condition; processor speed |
| Dot gain higher than expected | Focus out of adjustment; linearisation curve out of date | Measure 10%, 50% and 90% patches with a plate reader; re-linearise |
| Uneven density across the plate | Uneven developer flow or brushes; exposure uniformity | Processor brushes and spray bars; a full-plate tint test |
| Scratches or marks in the image | Handling, slip sheet residue, dirty rollers | Loading routine; processor roller cleaning |
| Image breaks down with UV ink | Our CTcP plate is not UV-ink resistant | Switch to double-layer thermal or trial processless; baking does not fix this |
For more fault-finding, see our CTP plate troubleshooting guide and the plate processor maintenance checklist.
Equipment and consumables for a CTcP line
A CTcP plate room needs the platesetter, a processor, developer and gum, and optionally a baking oven, punch and bender. We manufacture plates, processors, developer, baking ovens, punches and benders in our own factory. UV platesetters are supplied with our partner factories, with engineer installation on site, or remote video guidance and manuals for export customers, confirmed in the quotation.
| Item | Role | Source |
|---|---|---|
| CTcP plate | Positive-working UV-sensitive offset plate | Made in our factory |
| UV platesetter | Images the plate from the 1-bit TIFF | Supplied with our partner factories |
| Plate processor | Develops, rinses, gums and dries | Made in our factory |
| Developer | Removes the exposed coating | Made in our factory |
| Plate gum | Protects the non-image area | Supplied with our partner factories |
| Baking oven | Optional; hardens the plate for longer conventional-ink runs | Made in our factory |
If you are planning a new CTcP line or replacing film, send us your plate size, plates per day, press models and ink types. We will match the platesetter, processor, plate and developer as one system so the process is stable from the first plate.
FAQ
What is the CTcP process?
CTcP (computer to conventional plate) images a UV-sensitive offset plate directly with UV light from a 1-bit TIFF, then the plate is developed, rinsed, gummed and dried. It removes film and contact copying.
What is the difference between CTcP and thermal CTP?
CTcP images UV-sensitive plates with UV light and needs yellow safelight before development. Thermal CTP images heat-sensitive plates with an 830 nm infrared laser and allows room-light handling within TDS limits. CTcP plates are usually lower in cost.
What developer temperature is used for CTcP plates?
Our CTcP plate uses a standard PS-type developer at about 23 ± 2 °C. Keep temperature, conductivity and replenishment stable, and follow the grade TDS.
Is a CTcP plate positive or negative?
Our CTcP plate is positive-working. The exposed coating is removed in the developer and becomes the non-image area; the unexposed coating stays as the image.
Can CTcP plates be baked?
Yes. Our CTcP plate can be baked for longer runs with conventional inks, at the temperature and dwell time in the grade TDS. It is not UV-ink resistant, even after baking; for UV inks use a double-layer thermal plate or trial a processless plate.
Why do CTcP plates lose highlight dots?
Usually exposure energy is too high, or the developer is too hot, too strong or the dwell is too long. Check exposure with a step wedge, bring the developer back to the TDS condition, then re-linearise the RIP.
Setting up or tuning a CTcP plate room? Request a quote — send your plate size, plates per day, press models and ink types. Or request trial plates / contact us.
Disclaimer: values on this page are typical and for reference only; final specifications, MOQ, price and lead time are subject to the grade TDS and the quotation.
