Natural Colour Extraction Plants

Bark - Oak Bark / Birch

Mechotech designs and manufactures turnkey natural colour extraction plants for oak bark and birch bark, listed in the Brown Colour group. Both barks are tannin-rich: oak is dominated by ellagitannins and gallotannins, which carry the brown colour and the dyeing and tanning strength, and birch adds its own tannins. See the Brown Colour page for the group and the article on brown colour extraction from oak and birch bark.

Mechotech's Bark - Oak Bark / Birch plant is configured around the specific chemistry and processing requirements of Bark - Oak Bark / Birch. Built in SS 316L with integrated solvent recovery, automation, and full documentation, each plant is delivered as a commissioned turnkey system. Bark is dense, so the line is built around chipping or milling to expose the tannin-rich tissue, repeated leaching because a single pass leaves tannin bound in the bark, and vacuum concentration; the tannin pigment is described as heat-tolerant, so concentration and drying are undemanding.

Technical Specifications

Product	Bark - Oak Bark / Birch Extraction Plant
Raw Material	Oak bark and birch bark (catalogue name: Bark - Oak Bark / Birch)
Botanical Name	Quercus spp. (oak) and Betula spp. (birch) — genus level, per Mechotech’s brown-colour article; the species are not stated in the catalogue
Plant Part / Feed Form	Bark (a forestry or timber by-product, per the article); chipped, shredded or milled before extraction; exact form confirmed with the client
Colour Group	Brown Colour (see the Brown Colour page)
Colour-forming Components	Tannins — oak: ellagitannins and gallotannins (releasing ellagic and gallic acid); birch: tannins, with betulin in the pale outer bark (a white triterpene that accompanies the extract rather than colouring it)
Process Category	Natural Colour Extraction Plants
Extract Type	Standardised dry extract (powder)
Extraction Method	Hot-water leaching (article reference: typically 80 to 100 °C with several successive leaches) or food-grade alcohol / aqueous solvent in closed jacketed SS 316L extractors; the route is confirmed during process development
Product-contact Material	SS 316L, electropolished, CIP-cleanable
Filtration System	Plate-and-frame filter press with cartridge polish filtration
Concentration System	Falling-film / vacuum evaporator with closed-loop solvent recovery
Drying System	Spray dryer or vacuum dryer
Utility Requirements	Steam, chilled/cooling water, vacuum, compressed air, soft water, power (project-specific)
Automation	PLC-based automation
Plant Capacity	Configured to requirement
Compliance	GMP hygienic design; full documentation for qualification
Final Product Form	Free-flowing standardised extract powder

Plant Capacities

Plant Scale	Raw Material Throughput	Typical Use
Pilot	Configured to your feedstock and trial plan	Product development, parameter validation
Semi-Commercial	Configured between pilot and commercial scale	Contract manufacturing, scale-up trials
Commercial	Configured to raw-material supply and confirmed buyer volume	Commercial production at confirmed buyer volume

Capacity is configured to raw-material supply and confirmed buyer volume; we recommend a pilot plant to validate process parameters before scaling.

Manufacturing Process

Raw Material Preparation

Oak and birch bark is cleaned of dirt and debris and chipped, shredded or milled to expose the tannin-rich tissue, because intact bark releases its tannin slowly; the particle size is set during process development.

Extraction

The prepared bark is leached with hot water (the article gives typically 80 to 100 °C over an extended contact time) or with food-grade alcohol / aqueous solvent in closed jacketed SS 316L vessels, with several successive leaches because a single pass leaves much tannin bound in the tissue; the route and conditions are set during process development.

Filtration

The extract (miscella) is clarified through a plate-and-frame filter press followed by cartridge polish filters.

Concentration & Solvent Recovery

The miscella is concentrated in a falling-film / vacuum evaporator, with solvent recovered through the condenser return system.

Standardisation

The concentrate is assayed and adjusted to the declared target specification before drying.

Drying & Quality Control

The standardised Bark - Oak Bark / Birch extract is spray- or vacuum-dried, then released after assay, residual-solvent, heavy-metal, microbial, and moisture testing.

Major Plant Equipment

Raw material authentication, cleaning and moisture testing
Mill (size reduction)
Jacketed SS 316L extraction vessels
Plate-and-frame filter press
Cartridge polish filters
Falling-film / vacuum evaporator
Closed-loop solvent recovery system (condenser return)
Spray dryer / vacuum dryer
CIP (clean-in-place) system
PLC-based automation panel

Plant Output

Bark - Oak Bark / Birch extract — standardised to the declared target specification

Applications

Natural brown colourant and dye ingredient supply
Natural dyeing of wool, silk, cotton and linen across the brown-to-black range through mordanting (per the article)
Vegetable tanning of leather with oak-bark tannins (per the article)
Tannin-rich natural extract supply

Key Features

SS 316L Construction
Electropolished SS 316L product-contact surfaces with CIP operation between batches.
Closed-Loop Solvent Recovery
Integrated condenser-return recovery reuses solvent between batches and reduces solvent loss.
Standardised to Specification
In-process and batch-release assay are used to check the finished colour extract against the agreed target specification, such as shade and colour strength.
Integrated Drying
A matched spray/vacuum dryer produces a free-flowing, low-moisture powder ready for encapsulation and blending.
Scalable Batch Capacity
Plants are configured to requirement from pilot scale upward, with modular expansion.

Frequently Asked Questions

Does Mechotech supply the complete machinery for Bark - Oak Bark / Birch?

Yes. Mechotech supplies the complete turnkey plant for Bark - Oak Bark / Birch — engineered, fabricated at our Hyderabad facility, installed, and commissioned as a single integrated system.

What specification can the Bark - Oak Bark / Birch plant achieve?

The plant is configured to the client’s target specification for Bark - Oak Bark / Birch; the specification achieved is established during process development and pilot validation, and batch-release testing with certificate-of-analysis documentation is defined with the client.

What production capacities are available for the Bark - Oak Bark / Birch plant?

Capacity for the Bark - Oak Bark / Birch plant is configured to raw-material supply, confirmed buyer volume and investment timeline, starting at pilot scale; a pilot plant is recommended to validate parameters before scaling.

Which industries use the Bark - Oak Bark / Birch plant?

The end-use areas listed for Bark - Oak Bark / Birch on this page are given under Applications. The end use and the target specification are confirmed with the client before the plant is configured.

How is Bark - Oak Bark / Birch extract produced in Mechotech's extraction plant?

Raw material is authenticated, moisture-tested and milled, then extracted with food-grade solvent (alcohol / aqueous) in closed jacketed SS 316L extractors over multiple cycles. The miscella is clarified through a plate-and-frame filter press and cartridge polish filters, concentrated in a falling-film / vacuum evaporator with closed-loop solvent recovery, standardised, and spray- or vacuum-dried; each batch is released after assay, residual-solvent, heavy-metal, microbial and moisture testing. The line sits within Mechotech's Natural Colour Extraction Plants range.

What gives oak and birch bark their brown colour?

According to Mechotech’s article, the brown comes mainly from tannins: oak bark is rich in ellagitannins and gallotannins, historically called quercitannic acid, and birch bark contributes its own tannins; the article describes these pigments as pH-stable and heat-tolerant. Betulin from the pale outer birch bark is a white triterpene that accompanies the extract but is not the colourant.

Can an oak or birch bark extract give black as well as brown?

The article states that mordants steer the shade: alone the extract dyes in warm tan to rich brown, an alum mordant gives lighter golden-warm browns and an iron mordant forms dark iron-tannin complexes that shift the colour toward grey, slate, charcoal and near-black. The shade achieved on a given fibre or product is established in application trials.

How does this page relate to the Brown Colour and other bark pages?

This page covers oak and birch bark as a raw material of the Brown Colour group, which also lists coffee grounds, dandelion roots, ivy woody stems, walnut hulls (Hulls - Walnut) and yellow dock roots. Bark from sycamore is listed separately as Bark - Sycamore in a different colour group.

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Bark - Oak Bark / Birch