The Donut Probe for screen printers is a tool for measuring the temperature of the dryer from start to finish. This allows us to accurately determine the exact temperature of the colour fixation of the printed garment in the oven and guarantee that the print will withstand washing.


Many screen printers experience the issue of ink washing out after being laundered, which is often mistakenly blamed on the ink itself. In reality, the problem stems from not curing the ink sufficiently. This is a widespread and costly error within the screen printing industry. The Donut Probe is a valuable tool that precisely measures the temperature of the ink during the curing process. By using the Donut Probe, printers can accurately determine when the ink has reached the appropriate temperature for proper curing, thus preventing the ink from washing out and ensuring the print’s quality and durability.
Working with the Donut Probe
Ink & Curing Time
Proper ink curing is crucial for quality screen printing. Plastisol inks typically require one second at 160°C (320°F) to cure, whereas water-based inks need about 3 minutes at that temperature to fix properly. However, simply putting a garment into a 160°C dryer does not instantly raise it to that temperature – it takes time to heat the fabric and ink to the needed curing point.
As the video explains, ink curing only starts when 160°C is reached inside the dryer. By showing exactly how long printed goods are exposed to each temperature level inside the dryer, the donut probe enables dialing in optimal cure cycles. It helps ensure inks receive adequate heat and dwell time to fully crosslink, preventing problems with wash fastness, flexibility, and durability down the line.
Please note – in the video, the 160°C temperature shown for plastisol ink curing is accurate. However, for water-based inks, the 3 minute cure time at 160°C starts only AFTER the ink reaches this temperature, not from the beginning of the curing process. With water-based inks, the full 3 minutes at 160°C is required from the point the ink first hits this cure temperature in order to properly set the ink. So while 160°C may be referenced for both ink types in the video, the cure time requirements differ between plastisol and water-based. For water-based curing, the 3 minute countdown starts from 160°C onward.
When curing screen printed inks, remember that ink thickness and color impact required cure time:
- Thick ink deposits take longer to cure than thin ink. The full thickness must reach cure temperature.
- White and metallic silver inks reflect more heat and thus cure slower than dark ink colors.
- Allow extra cure time for prints with thick ink deposits, especially white/metallic ink on dark garments. The donut probe helps validate optimal cure cycles.
- Adjust the curing times downwards for thin ink layers on light coloured garments by increasing the belt speed rather than lowering the temperature.
Properly mapping temperature profiles with a donut probe provides crucial data to set ideal cure times for each ink/substrate combination. This prevents under or over-curing. Consistently monitoring cure temperatures is key for quality assurance.
Mapping a Screen Printing Dryer with a Donut Probe
Why we should use the Donut Probe to Map a dryer: To detect faulty heating elements or airflow blockages. A donut probe can identify drops of 5°C/10°F that indicate issues with heating units. Mapping makes these problems visible.
- Download a dryer mapping template
- Fill in basic information like dryer name, date, belt speed, and heating methods
- Place the probe at the beginning of the infeed belt and note the location
- Repeat probe placement at the right and left sides of the infeed
- Have an assistant take readings every 5 seconds and record on the template
- Note temperature, duration at each temp, and any drops
- Map the entire length of the belt from inlet to outlet
- Check both left and right sides – one side may be cooler

Mapping a Dryer
The key reasons mapping a dryer with a donut probe helps are:
- Detecting faulty heating elements (drops of 5°C/10°F)
- Detecting airflow blockages
Proper curing is critical for quality screen printing, and the donut probe is an indispensable tool for validating cure cycles. It provides accurate dryer temperature readings from inlet to outlet to ensure inks reach the fully cured state.
Inexperienced screen printers often fail to cure ink correctly, which leads to washout and reduced print quality from cracking or poor adhesion. By mapping the exact thermal profiles inside the dryer, the donut probe gives assurance that prints withstand washing. It helps detect issues like faulty heating elements (drops of 5°C) or airflow inconsistencies.
With the ability to monitor temperature and duration at each point, the donut probe is essential for professional screen printing quality assurance. It also finds temperature fluctuations indicating problems. Ensuring inks cure at the correct temperature for the fully recommended time prevents common quality issues.
Price under 480 $ : Spend to Save
Here’s a smart way to maximize your savings: Instead of purchasing the Screen Printer Donut Probe as a single unit, consider buying the tester and probe separately. While the combined set typically costs $482, purchasing them individually amounts sometimes to $383, offering a savings of nearly $100!
Moreover, investing in a Donut Probe is not as expensive as it might seem when considering its value in preventing costly mistakes. For instance, if a t-shirt costs $2.50 and you face 200 T-Shirts claims due to ink washing out, the Donut Probe, priced at $500, would have already paid for itself by averting these issues.
Where can you buy it and at what prices?

Infrared Guns: Not a Reliable Substitute!
Infrared temperature guns are commonly used in the screen printing department as a replacement for the donut probe. However, it is important to recognize that the infrared temperature gun is NOT a reliable substitute for the donut probe.
The key reasons an IR gun alone is insufficient, based on the search results, are:
- It only measures ink surface temperature, not internal temp through the full ink thickness.
- It does not indicate the duration ink is at curing temperature like a donut probe.
- Its reflective readings can be much higher than actual ink temp.
- Airflow and distance to ink impact IR gun accuracy.
- Can’t map a dryer
Download the manual of a Donut Probe
Keep Reading
A Comprehensive Donut Probe GuideSummary
In summary, the Screen Printer Donut Probe is vital for screen printers to accurately monitor dryer conditions. Proper mapping and curing validation with a donut probe significantly improves print durability and wash-fastness. It is a crucial investment for consistency and profitability.
Questions & Answers
What is a donut probe?
A donut probe is a temperature measurement tool used in screen printing. It accurately measures the temperature of inks by reading the contact temperature between two crossed wires. This provides precise temperature readings for printers to determine optimal cure temperatures and times, ensuring quality results. Donut probes are essential for achieving accurate temperature control in the printing process.
How does the Donut Probe help with curing ink?
The Screen Printer Donut Probe helps to cure ink by monitoring and controlling the temperature of the dryer from the inlet to the outlet. It allows us to accurately determine the temperature of the t-shirt when printed, guaranteeing that the printing ink is wash resistant. By mapping the dryer, the Donut Probe can also detect any temperature drops, which could indicate a broken curing panel or a blockage in the airflow.
What is the difference between the Donut Probes and the Infrared Temperature Guns?
The difference between the Donut Probes and the Infrared Temperature Guns is that the Donut Probe provides more accurate temperature readings of the dryer, from the inlet to the outlet, and can be used to detect defective heating elements in the dryer. The Infrared Temperature Gun is not a viable substitute for the Donut Probe as it cannot provide accurate readings of the dryer, and cannot be used to detect any defective heating elements. Additionally, the Donut Probe can also be used to ensure that the ink gets the proper temperature for the recommended time, whereas the Infrared Temperature Gun cannot.
Hello
Sir
I need this donut prob can you tell me where from I get this
Thanx
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Regards
Stefan