Procion Reactive Dyes in Textile Printing
Part 2: One-Stage and Two-Stage Printing Processes Explained
In Part 1, we understood the basic nature of Procion reactive dyes, their classification, and the ingredients used in a typical printing paste. We saw that Procion dyes are suitable for cotton and viscose because they form a chemical bond with cellulose fibres under alkaline conditions.
Now we come to the next important question:
In Procion dye printing, the key point is not only which dye is used, but also when alkali is introduced into the system. This gives rise to two broad methods of printing:
- One-stage process
- Two-stage process
Understanding this difference is very important because it affects paste stability, fixation, shade development, and print quality.
Why Alkali Timing Matters
In reactive dye printing, alkali plays a central role. It activates the reaction between the dye and the cellulose fibre.
But alkali also creates a practical problem.
Once alkali is mixed with the dye paste, the dye becomes more active. This means the dye may start reacting or losing strength even before it reaches the fabric. Therefore, the timing of alkali addition becomes very important.
Alkali is necessary for fixation, but if introduced too early, it can reduce paste stability.
This is why textile printers choose either a one-stage or two-stage process depending on the dye class, production requirement, and available equipment.
One-Stage Process
In the one-stage process, alkali is already present in the printing paste.
The fabric is printed with this complete paste, and then the printed fabric is fixed by a process such as:
- Steaming
- Baking
Since dye and alkali are present together in the same paste, the system is ready for reaction once the right moisture, temperature, and time are provided.
How the One-Stage Process Works
The general sequence is:
- Prepare the printing paste with dye, thickener, urea, resist salt, water, and alkali.
- Print the fabric.
- Dry the printed fabric.
- Fix the colour by steaming or baking.
- Wash the fabric to remove unfixed dye and auxiliaries.
This method is convenient because the printing paste already contains the necessary ingredients for fixation.
Advantages of the One-Stage Process
The one-stage process is relatively simple to understand and operate.
Its advantages include:
- Fewer processing steps
- Alkali is already present in the paste
- Suitable for processes where immediate fixation is planned
- Convenient for steaming or baking-based fixation
However, the limitation is that the paste may not remain stable for long, especially when highly reactive dyes are used.
Limitation of the One-Stage Process
The biggest limitation is paste stability.
If the dye is highly reactive, the presence of alkali in the paste may make the paste unstable. This is especially important in the case of Procion-M dyes.
Procion-M dyes are highly reactive. Therefore, their paste should not be prepared too much in advance. It should be prepared only in the quantity needed for immediate printing.
Two-Stage Process
In the two-stage process, the printing paste is prepared without alkali.
The alkali is applied separately, either before or after printing.
This means the dye paste remains more stable because the chemical trigger, alkali, is not present in the paste at the beginning.
How the Two-Stage Process Works
There are two possible approaches.
1. Alkali Before Printing
The fabric may be treated with alkali first, dried, and then printed with dye paste that does not contain alkali.
This approach is seen in processes such as air-hanging, where the fabric may be padded with soda ash before printing.
2. Alkali After Printing
The fabric may first be printed with a paste that does not contain alkali. After printing and drying, the alkali is applied by padding or another suitable method.
This approach is used in processes such as:
- Flash ageing
- Vat development
- Pad alkali–batch process
Advantages of the Two-Stage Process
The two-stage process gives better control over the reaction.
Its advantages include:
- Better paste stability
- Cleaner printing in many cases
- Useful where the printed fabric has to be stored before development
- Better control over fixation
- Suitable for processes where alkali is applied separately
In this method, the dye and alkali are kept apart until the required stage. This prevents premature reaction and helps maintain paste quality.
One-Stage vs Two-Stage Process
| Point | One-Stage Process | Two-Stage Process |
|---|---|---|
| Alkali position | Present in printing paste | Applied separately |
| Paste stability | Lower, especially with reactive dyes | Better |
| Process simplicity | Simpler | More controlled but involves an extra step |
| Fixation method | Usually steaming or baking | Alkali treatment before or after printing |
| Best suited for | Immediate fixation | Controlled fixation and better paste life |
Paste Stability of Different Procion Dyes
The stability of printing paste depends largely on the reactivity of the dye.
Procion-H and Procion-Supra
The paste of Procion-H and Procion-Supra dyes can remain usable for a long time, up to about 28 days.
This is because these dyes are not as highly reactive as Procion-M.
Procion-H is the least reactive among the three groups, so its paste stability is good. Procion-Supra has intermediate behaviour and also shows reasonable paste stability.
Procion-M
The paste of Procion-M does not remain stable for long.
Because Procion-M dyes are highly reactive, their paste should be prepared only as much as required.
This is a very practical production point.
If Procion-M paste is prepared in excess and stored for too long, the dye may lose its effectiveness and the final print may suffer.
Compatibility of Procion Dye Classes
Most Procion dyes can be used together to obtain different shades. However, compatibility depends on their reactivity.
Procion-H and Procion-M dyes should not normally be used together.
This is because Procion-H is slow-reacting, while Procion-M is highly reactive. Their fixation behaviour is different, and this may create difficulty in obtaining proper shade development.
Procion-Supra and Procion-H can be used together.
This is because their behaviour is more compatible in practical printing conditions.
Role of Resist Salt in Procion Printing
During roller printing, it has been observed that colour may sometimes go to the back side of the fabric. This can affect the appearance and quality of the print.
To control this problem, resist salt is used.
Resist salt helps in preventing unwanted effects during printing and is especially useful where controlled print definition is required.
It is also used in discharge printing.
Resist Salt and Discharge Printing
In discharge printing, a reducing or discharge agent removes colour from selected areas of the fabric.
However, one practical problem may occur.
Sometimes the discharge effect does not remain limited only to the printed area. The surrounding area may also get affected. This can spoil the sharpness of the design.
To prevent this, the fabric may be treated before printing with a mild oxidizing agent.
Examples include:
- Sodium nitrobenzene sulphonate
- Sodium chlorate
These chemicals help neutralize the unwanted effect of reducing or discharge agents that may spread beyond the printed area.
Why Oxidizing Agents Are Used
If a discharge or reducing agent comes out from the printing paste and spreads to surrounding areas, it may unintentionally affect the fabric.
When the fabric has already been treated with a mild oxidizing agent, the reducing effect is reduced or neutralized.
The oxidizing agent protects the surrounding fabric from unwanted discharge.
This helps maintain cleaner print boundaries and reduces accidental damage to nearby areas.
Foam Control in Printing Paste
Sometimes chemicals may also be added to the printing paste to prevent foam formation.
Foam can create problems during printing because it may lead to uneven application, spots, weak print areas, or poor design clarity.
Therefore, foam control is another small but important part of printing paste management.
Development After Printing
After the fabric is printed and dried, the colour has to be developed or fixed.
The main development methods include:
- Steaming
- Baking
- Flash ageing
- Air-hanging
- Vat development
- Pad alkali–batch process
These methods will be discussed in detail in Part 3.
Printing applies the dye design, but development fixes the dye onto the fibre.
Without proper development, the dye may remain unfixed and may wash out.
Practical Understanding for Students
The difference between one-stage and two-stage printing is not merely a process detail. It is a way of controlling the chemistry of reactive dye printing.
In one-stage printing, the dye and alkali are together in the paste. This makes the process simpler, but paste stability can become a concern.
In two-stage printing, dye and alkali are kept separate until the desired stage. This improves control and paste stability but adds another process step.
The printer must balance:
- Dye reactivity
- Paste stability
- Print sharpness
- Fixation method
- Production timing
- Available machinery
This is why textile printing is both a chemical and practical craft.
Common Mistake
A common mistake is to think that alkali should always be added directly into the printing paste.
That is not always true.
In many processes, alkali is deliberately kept out of the paste and applied separately. This is done to improve paste stability, print quality, and process control.
Knowledge Nugget
In Procion dye printing, alkali is the trigger, but timing is the control.
Adding alkali at the right stage is one of the most important decisions in the printing process.
Reflection Question
Why does a two-stage process generally give better paste stability than a one-stage process?
The answer is simple:
Because the dye and alkali are kept separate until the desired stage of fixation.
Disclaimer and Safety Note: This article is intended for educational and informational purposes only. The recipes, chemical names, quantities, temperatures and process conditions mentioned here are provided to explain the principles of Procion reactive dye printing and should not be treated as direct instructions for unsupervised practical use. Textile printing involves the use of dyes, alkalis, salts, thickeners and other auxiliary chemicals, which should be handled only with proper knowledge, suitable safety precautions and appropriate supervision. Before using any chemical, always refer to the latest supplier technical data sheet, safety data sheet and applicable local regulations. Use appropriate personal protective equipment, ensure good ventilation, safe storage, careful measurement, spill control and responsible disposal of chemical residues and wastewater. The author and publisher do not accept responsibility for any loss, damage, injury or environmental harm arising from the direct or indirect use of the information given in this article, and readers are advised to consult trained textile processing professionals before attempting any laboratory or industrial application.
Goyal, P. Procion Reactive Dyes in Textile Printing - Part 2: One-Stage and Two-Stage Printing Processes Explained. My Textile Notes. Available at: http://mytextilenotes.blogspot.com/2026/05/procion-reactive-dyes-in-textile.html
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