Whether you’re a DIY enthusiast, small business owner, or professional print shop operator, screen printing involves more than just pushing ink through a screen. Behind every perfect print lies a careful mix of chemistry and technique.
Understanding which chemicals are used in screen printing is essential—not just for creating better prints, but for maintaining equipment, ensuring operator safety, and complying with environmental regulations.
Basics of Screen Printing
Screen printing is a versatile technique that uses a mesh screen, ink, and a stencil to transfer a design onto a substrate most commonly fabric, but also wood, metal, paper, and plastics.
The key steps in screen printing include:
- Preparing the screen
- Applying emulsion
- Exposing the emulsion with a design
- Washing out the design
- Printing with ink
- Cleaning and reclaiming the screen
Each of these steps involves specific chemicals tailored to improve accuracy, durability, or efficiency.
Types of Chemicals Used in Screen Printing
Let’s categorize the most commonly used screen printing chemicals by their type and purpose.
a. Emulsions
These are light-sensitive chemicals used to create the stencil. They’re applied to the mesh screen and hardened via UV exposure. More on this below.
b. Sensitizers
Used to activate certain types of emulsions (like diazo). They make the emulsion light-sensitive.
c. Degreasers
Clean the mesh before applying emulsion. They remove oils, dust, and residue to ensure emulsion adheres properly.
d. Screen Openers
Spray-on or liquid chemicals that dissolve dried or clogged ink in mesh openings during production.
e. Ink Removers
Also known as ink wash or ink degraders, these remove leftover ink from the screen after printing.
f. Stencil Removers
These solutions break down and take off the solidified emulsion from the screen, making it ready to use again.
g. Ghost/Haze Removers
Chemicals that eliminate stubborn “ghost images” or stains left after emulsion removal.
h. Adhesives & Tack Sprays
Used to hold the substrate (like a T-shirt) in place on the press pallet during printing.
Detailed Look at Emulsions and Sensitizers
Emulsions are one of the most important parts of the screen printing process.
a. Diazo Emulsion
- Most common and beginner-friendly.
- Comes with a separate sensitizer (diazo powder) that must be mixed in before use.
- Slower exposure time but more forgiving.
- Yellow-green in color.
b. SBQ Photopolymer Emulsion
- Pre-sensitized, no mixing required.
- Fast exposure times (2–4x faster than diazo).
- More sensitive to light; requires careful handling.
- Violet or pinkish in color.
c. Dual Cure Emulsion
- Combines properties of diazo and SBQ.
- Offers excellent detail resolution and solvent resistance.
- Preferred for complex or multicolor jobs.
Sensitizers (Diazo)
- A chemical component added to emulsions to make them UV-reactive.
- Typically come as powder in small bottles, mixed with water and added to emulsion base.
Screen Cleaning and Reclaiming Chemicals
After printing, screens must be cleaned and reclaimed for reuse. This involves multiple chemical stages:
a. Ink Wash/Degraders
- Break down the ink so it can be washed away with water.
- Comes in citrus-based (eco-friendlier) and solvent-based formulas.
b. Emulsion Removers
- Dissolve hardened stencil emulsions.
- Usually applied with a scrub pad, then rinsed under pressure.
c. Haze/Ghost Removers
- Strong chemicals designed to remove residue images or stains.
- Often caustic—must be used with proper safety gear.
d. Degreasers
- Used again after reclaiming to prep the screen for a new emulsion layer.
- Helps ensure consistent emulsion adhesion.
Inks and Their Chemical Composition
Inks themselves are chemical-based products and selecting the right one is critical to your workflow.
a. Plastisol Inks
- Most commonly used in garment screen printing.
- PVC-based, thick, and requires heat curing (~320°F/160°C).
- Does not dry on screens but may require solvent for cleanup.
b. Water-Based Inks
- Penetrate fabric fibers, giving a soft hand feel.
- Air-dry or heat-cure.
- Can dry in screen; needs proper screen maintenance.
c. Discharge Inks
- Contain chemicals (formaldehyde-based activators) that bleach existing fabric dye before applying new color.
- Suitable for darker garments.
- Require excellent ventilation.
d. Solvent-Based Inks
- Used in non-textile screen printing (e.g., glass, metal, plastics).
- Dry quickly via solvent evaporation.
- Require heavy-duty chemical cleanup and strong ventilation.
Environmental and Safety Considerations
Using screen printing chemicals requires safe practices and environmental awareness.
a. Ventilation
- Make sure you operate in a place with good air flow to avoid breathing in dangerous pollutants.
- Spray booths or vented reclaiming stations are recommended.
b. Personal Protective Equipment (PPE)
- Gloves (nitrile), goggles, aprons, and sometimes respirators should be used.
- Especially important when working with strong haze removers or solvent-based inks.
c. Disposal
- Screen printing chemicals should never be poured directly into the drain.
- Use approved waste disposal systems or contract with chemical waste handlers.
- Look for eco-friendly, biodegradable options when possible.
How to Choose the Right Chemicals for Your Screen Printing Operation
Your chemical selection depends on several factors:
| Factor | Consideration |
| Type of Printing | Textile vs hard-surface printing |
| Ink Used | Plastisol vs water-based |
| Frequency | Occasional use vs high-volume |
| Screen Reuse | One-time use or reclaim and reuse? |
| Budget | Professional-grade vs DIY solutions |
| Environment | Access to ventilation, drain systems, etc. |
If you’re starting out:
- Use diazo emulsion for flexibility.
- Opt for water-based degreasers and ink removers for safer and easier handling.
Go for plastisol inks if you have access to a heat press or conveyor dryer.
FAQs
Q: Are screen printing chemicals toxic?
Many are hazardous if improperly handled, especially solvents and haze removers. Always use PPE and follow safety guidelines.
Q: Can I use household products as substitutes?
Some DIYers use bleach or simple green for cleaning screens, but this is not recommended for professional results or long-term screen health.
Q: Are there eco-friendly options?
Yes—look for citrus-based cleaners, biodegradable ink washes, and water-based inks with low VOC content.
Q: What’s the shelf life of emulsions?
- Diazo (after mixing): ~4–6 weeks
- SBQ: 6–12 months unopened
- Dual Cure: ~3 months after mixing
Q: How should chemicals be stored?
Keep it in a cool, dry, and dark place, like a cabinet that is safe for chemicals. Label all containers clearly.
Conclusion
Screen printing is as much a science as it is an art, and the chemicals you choose play a massive role in the quality, durability, and efficiency of your prints. From emulsions and sensitizers to ink removers and haze cleaners, each chemical has a specific function that supports the overall process. By understanding the purpose and properties of these chemicals, you can optimize your workflow, protect your equipment, and ensure safer working conditions. Whether you’re printing a handful of tees in your garage or running a high-volume shop, making informed chemical choices is a foundation for success.