Guide to Brush Bristle Straightening Process – Steam and Boiling
Pig Bristle Processing – High-Temperature Steam and Boiling Treatment
Guide teach you how to specialize in producing high-quality boiled and steamed pig bristle for professional brush applications. The process combines traditional bristle craftsmanship with precise temperature control to create straight, elastic and durable bristle bundles suitable for premium paint brushes and other technical brushes.
This page explains our full processing flow, from aluminum tube loading to thermal treatment, sorting, and final packing, so buyers can clearly understand how we control quality at every step.
1. Aluminum Tube Loading
After thorough washing and cleaning, the pig bristle is carefully inserted into conical aluminum tubes:
Bristle density is controlled: tight enough for shaping, but never over-packed.
The bristles are aligned straight and evenly; no hair is allowed to protrude from the tube opening.
The aluminum tube works both as:
a mold to define final straightness and shape
a heat conductor to ensure even heating during boiling or steaming
This controlled tube loading step is the foundation of consistent straightness and shape stability.
2. Boiling Process – 100°C Water Treatment
Once filled, the aluminum tubes are placed into woven bags and loaded into boiling baskets. They are then fully submerged in boiling water at 100°C, with the water level kept at least 10 cm above the top of each tube.
Boiling time depends on bristle length and color:
Black bristle, 51–70 mm: approx. 6–7 hours
Black bristle, 76 mm and above: approx. 7–8 hours
White bristle, 51–70 mm: approx. 4–5 hours
White bristle, 76 mm and above: approx. 5–6 hours
After boiling:
The tubes are moved to a drying room.
Drying temperature is controlled at 90–100°C.
Drying time is typically 48–52 hours.
After cooling, the bristles are removed from the tubes for the next processing stage.
This long, stable boiling and drying process helps set the bristle, improve straightness and reduce microbiological risk.
3. High-Temperature Steam Treatment
For selected grades and specifications, we use high-temperature steam instead of (or in addition to) water boiling:
Steam chamber temperature: 105–110°C
Treatment time: usually 1–2 hours
Under these conditions, the steam gently softens the keratin structure of the bristle. This allows naturally curved or wavy hairs to relax and straighten without damaging their natural elasticity.
Immediately after steaming:
The hot bristles are quickly loaded into aluminum tubes again.
They cool and set inside the tube, locking in a smooth, straight profile.
This combination of high-temperature steam and aluminum tube setting gives the bristle a refined appearance with excellent resilience and shape memory.
4. Sorting and Blending
After thermal treatment (boiling and/or steaming), the bristles are carefully graded and blended:
Bristles are sorted by length and color into different grades.
According to customer requirements, different grades are blended in set ratios to control quality, color uniformity, and cost.
The material is then processed on combing and reversing equipment so that approximately 75% of roots and tips are correctly separated, forming clean semi-finished bundles.
This professional grading and blending step ensures stable specifications from lot to lot.
5. Finishing and Packing
In the finishing department, our skilled workers carry out detailed manual operations to achieve consistent, ready-to-use bundles:
Hand-rolling to remove reversed hairs and irregular roots
Iron-clamp length setting to keep length and grade accurate
Combing and trimming to create neat, uniform bundles
Tip hanging and root polishing for better brush-making performance
Packing standards:
Bundles are tightly wrapped to be firm, flat, and not loose.
Standard carton packing: 25 kg net weight per carton (with a narrow tolerance).
Each carton is labeled with lot numbers for full quality traceability.
6. Product Features and Benefits
Thanks to our combination of water boiling, high-temperature steam, and aluminum tube shaping, our pig bristles offer:
Excellent straightness and smoothness – ideal for high-quality paint brush production
High elasticity and long-term shape stability – bristles recover well after bending
Clean, odorless, low-impurity texture – better user experience and easier brush manufacturing
Stable color and gloss – can be further bleached or dyed according to customer specifications
These features make the bristle suitable for professional paint brushes, industrial brushes, artist brushes, and other specialist applications.
7. Why This Process Matters for Brush Manufacturers
For brush makers, consistent bristle behavior is critical:
Straight, evenly set bristle bundles reduce waste in the brush workshop.
High elasticity helps brushes hold their shape and deliver smooth, controlled strokes.
Good cleanliness and low odor improve the final product’s perceived quality.
Stable grading and blending save time on in-house sorting.
By controlling each step—from aluminum tube loading, boiling and steaming, through to sorting and final packing—you can provide pig bristle that is ready for efficient, modern brush production.
