Methods of laboratory testing of wood preservatives against fungi and borers (powder post beetles) : Part 1 Determination of threshold values of wood preservatives against fungi

IS 4873 Part 1: Scope Overview

This part of IS 4873 covers specifications for metallic coated steel sheets used in general engineering and construction.

Key Points on Scope:

• Applies to metallic coated steel sheets with coatings like zinc, aluminium, or zinc-aluminium alloys.
• Specifies coating mass, mechanical properties, and test methods.
• Ensures compliance by rounding off values per IS 2:1960.
• Mass loss calculations (Clause 3.8) follow the procedure in Clause 2.10 (typically related to corrosion or coating thickness loss).

Important Notes:

• Values must be rounded to the same significant figures as specified.
• Mass loss formula (from 2.10) generally is:

[ \text{Mass Loss} = \frac{\text{Initial Mass} - \text{Final Mass}}{\text{Area} \times \text{Time}} ]

Summary Table (Typical Coating Masses):

flowchart LR
    A[Steel Sheet] --> B{Coating Type}
    B --> C[Zinc]
    B --> D[Aluminium]
    B --> E[Zinc-Aluminium Alloy]
    C --> F[Coating Mass Specified]
    D --> F
    E --> F
    F --> G[Mass Loss Calculation per IS 4873 2.10]

For exact values and test methods, refer to the full IS 4873 Part 1: 2008 document.

IS 4873 Part 1: Preparation of Test Samples

Key Clauses Summary:

• Clause 2.2: Preparation of Test Sample

  • Test samples must be prepared as per specified dimensions and conditions.
  • Samples should be representative of the material batch.
  • Avoid contamination or damage during preparation.

• Clause 2.7: Preparation of Test Culture

  • Test cultures must be prepared under controlled conditions to ensure consistency.
  • Follow sterilization and incubation protocols as per the standard.

• Clause 3.2: Conditioning of Test Blocks

  • Conditioning must follow the procedure in Clause 2.2.2 (typically involving controlled temperature and humidity).
  • Ensures uniform moisture content and temperature before testing.

• Rounding Off (IS 2:1960)

  • Final test results must be rounded off according to IS 2:1960.
  • Retain significant figures as per the specified value in the standard.

Typical Sample Preparation Specifications (General Practice):

Rounding Off Rules (IS 2:1960) Summary:

• If the digit to be dropped < 5, leave the last retained digit unchanged.
• If the digit to be dropped > 5, increase the last retained digit by 1.
• If the digit to be dropped = 5, round to make the last retained digit even.

flowchart TD
    A[Sample Collection] --> B[Sample Preparation (Clause 2.2)]
    B --> C[Conditioning (Clause 3.2)]
    C --> D[Test Culture Preparation (Clause 2.7)]
    D --> E[Testing]
    E --> F[Rounding off results (IS 2:1960)]

Note: For exact dimensions and detailed procedures, refer to IS 4873 Part 1:2008 full text.

IS 4873 Part 1: Treatment Procedure Summary

Treatment Steps (Clauses 2.4 & 3.3)

• Blocks placed in beaker under weight to prevent floating.
• Beaker placed in desiccator connected to manometer & suction pump.
• Create partial vacuum of 60 mm Hg for 30 min.
• Pour freshly prepared preservative solution into separating funnel; stem extends into beaker.
• Run preservative solution into beaker to fully cover blocks.
• Release vacuum; cover beaker with lid to prevent evaporation.
• Leave blocks for 30 min, then wipe excess and weigh immediately (W2).

Drying & Conditioning (Clause 2.2.2)

• Dry blocks in oven at 100–105°C to constant mass (W).
• Treat 12 blocks per preservative concentration.
• Leaching: Start 3 days after oil-type treatment, 14 days after water-borne.
• Leach 6 blocks for 14 days at 50°C (except 2 h/day at room temp for first 9 days).
• Condition 6 leached & 6 unleached blocks at 30°C, 70 ± 4% RH to constant mass (W3).

Retention Calculation (Clause 2.5)

[ \boxed{ R = \frac{G \times C \times 100}{V} \quad \text{(g/cm}^3\text{)} } ]

Where:

Retention can be converted to kg/m³ by multiplying g/cm³ by 1000.

Process Flow Diagram

flowchart TD
    A[Place blocks in beaker under weight] --> B[Place beaker in desiccator]
    B --> C[Create vacuum: 60 mm Hg for 30 min]
    C --> D[Add preservative solution to cover blocks]
    D --> E[Release vacuum, cover beaker]
    E --> F[Leave for 30 min]
    F --> G[Remove blocks, wipe,

Leaching Procedure (IS 4873 Part 1) Key Points

• Sample Preparation:

  • Dry blocks at 100–105°C to constant mass (W).
  • Use 12 blocks per preservative concentration.
  • Start leaching 3 days after oil-type treatment, 14 days after water-borne treatment.

• Leaching Setup:

  • Place blocks in beakers, weigh down with glass weights.
  • Add distilled water ≈ 9× block volume.
  • Remove blocks after 2 hours of leaching.
  • 6 blocks leached for 14 days at 50°C (except 2h at room temp on first 9 days).
  • 6 blocks remain unleached for comparison.
  • Condition all blocks at 30°C, 70 ± 4% RH.

• Soil Exposure (Clause 5.0):

  • Use 125 g sifted garden soil (pH 5.0–7.0) in 237 ml capped bottles.
  • Add distilled water to 130% water holding capacity.
  • Place 2 feeder blocks on soil surface.
  • Sterilize bottles at 0.1 N/mm² for 60 min on two consecutive days.

• Treatment Solution Absorption (Clause 2.4):

  [ G = W_2 - W_1 ]

  Where:

  • (W_1) = initial dry mass
  • (W_2) = mass after treatment and wiping excess

• Vacuum Treatment:

  • Partial vacuum of 60 mm Hg for 30 min.
  • Pour preservative solution to cover blocks.
  • Release vacuum and cover beaker.
  • Soak blocks for 30 min before weighing.

Summary Table for Leaching Conditions

IS 4873 Part 1: Preparation of Test Culture

Key Specifications (Clauses 2.6 & 3.5):

• Medium Composition:

  • Agar: 20 g/L
  • Malt Extract: 20 g/L
  • Distilled Water: 1 litre

• Preparation Steps:

  1. Dissolve 20 g agar + 20 g malt extract in 1 litre distilled water.
  2. Pour ~60 ml into each Kolle-flask.
  3. Plug flask with cotton wool.
  4. Sterilize by autoclaving at 0.1 N/mm² (120°C) for 20 minutes.
  5. After sterilization, lay flask flat so medium is retained by neck ridge.
  6. Inoculate with test fungus within 6 days post-preparation.
  7. Pour sterile water over cotton wool plug to maintain humidity.

Summary Table:

flowchart TD
    A[Prepare Medium: Agar + Malt Extract + Water] --> B[Pour 60 ml into Kolle-flask]
    B --> C[Plug with cotton wool]
    C --> D[Sterilize at 120°C, 0.1 N/mm² for 20 min]
    D --> E[Lay flask flat to retain medium]
    E --> F[Inoculate with test fungus (within 6 days)]
    F --> G[Pour sterile water over cotton wool to maintain humidity]

This ensures optimal fungal growth conditions for testing as per IS 4873 Part 1.

IS 4873 Part 1: Preparation of Soil Culture Bottles

Key Specifications (Clause 2.6)

• Soil: 125 g sifted, air-dried garden soil (pH 5.0 to 7.0)
• Bottle: 237 ml aluminum screw-capped bottle
• Soil Compaction: By tapping to fill bottle
• Water Addition: Distilled water to achieve 130% Water Holding Capacity (WHC)
• Feeder Blocks: Two blocks placed on soil surface (size as per code)
• Sterilization: Autoclave at 0.1 N/mm² (1 bar), 60 min, two consecutive days, caps loosened

Water Holding Capacity (WHC)

• WHC is the maximum water soil can retain against gravity.
• Add water = 130% × WHC × soil dry weight (125 g)

Nutrient Medium for Growing Culture (Clause 3.5)

• Composition per litre:
  • Agar: 20 g
  • Malt Extract: 20 g
• Pour ~60 ml into Kolle-flasks
• Sterilize at 0.1 N/mm² (120 ℃) for 20 min
• After sterilization, lay flask flat to retain medium
• Inoculate with test fungus within 6 days
• Maintain moisture by adding sterile water over cotton wool plug

Summary Table

flowchart LR
    Soil[Soil (125 g, pH 5-7)] -->|Fill &

IS 4873 Part 1: Medium for Growing Culture (Clause 3.5)

• Medium Composition:

  • Agar: 20 g
  • Malt Extract: 20 g
  • Distilled Water: 1 litre

• Preparation Steps:

  1. Mix agar and malt extract in distilled water.
  2. Pour ~60 ml into each Kolle-flask.
  3. Plug with cotton wool.
  4. Sterilize by autoclaving at 0.1 N/mm² (120°C) for 20 minutes.
  5. After sterilization, lay flask flat so medium is retained by the neck ridge.
  6. Inoculate with test fungus within 6 days.
  7. Pour sterile water over cotton wool pad to maintain moisture.

Additional Related Specifications:

• Soil Culture Bottles (Clause 5.0):
  • Soil: 125 g air-dried, sieved garden soil (pH 5.0–7.0)
  • Bottle Volume: 237 ml aluminium screw-capped
  • Water: Add distilled water to reach 130% water holding capacity
  • Feeder blocks placed on soil surface.
  • Sterilization: Autoclave at 0.1 N/mm² for 60 min on two consecutive days with caps loosened.

Summary Table:

flowchart TD
    A[Prepare Medium] --> B[Pour ~60 ml into Kolle-flask]
    B --> C[Plug with cotton wool]
    C --> D[Sterilize at 0

IS 4873 Part 1: Infection of Test Blocks - Key Specifications & Procedures

Infection Procedure (Clauses 2.8 & 3.6)

• Placement: Test blocks (cross-section face down) are placed aseptically on thin glass rod rings inside flasks with actively growing fungal cultures.
• Contact: Blocks contact aerial mycelium, not the culture medium, to avoid preservative leaching.
• Quantity: Max 2 blocks per flask.
• Humidity Control: Sterile water added in flask neck to maintain ideal moisture.

Incubation & Duration (Clause 2.9)

• Conditions: Incubate at 25 ± 1°C, 70 ± 4% RH for 12 weeks.
• Post-Incubation: Remove, clean mycelium carefully, weigh immediately if moisture content is needed.
• Drying: Dry in warm air, then condition at 30°C, 70 ± 4% RH to constant weight (W).

Treatment & Leaching (Clause 2.2.2)

• Blocks per concentration: 12 blocks.
• Leaching Start:
  • Oil-type preservatives: after 3 days.
  • Water-borne preservatives: after 14 days.
• Leaching Cycle: 6 blocks leached at 50°C for 14 days (except 2h daily at room temp for first 9 days).
• Conditioning: Both leached and unleached blocks conditioned at 30°C and 70 ± 4% RH.

Summary Table

flowchart LR
    A[Test Blocks Prepared] --> B[Placed on Glass Rod

IS 4873 Part 1: Incubation and Duration of Test

Key Specifications (Clauses 2.9 & 3.7)

• Incubation Conditions:

  • Temperature: 25 ± 1°C
  • Relative Humidity: 70 ± 4%
  • Duration: 12 weeks

• Procedure:

  • Place test blocks in bottles with feeder blocks (face down).
  • Incubate in specified conditions for 12 weeks.
  • After incubation, remove blocks, clean off mycelium carefully without removing wood splinters.
  • Immediately weigh if moisture content is to be determined.
  • Dry blocks in warm air, then condition at 30°C and 70 ± 4% RH until constant weight (W).

Summary Table

Notes:

• Follow preparation (2.7) and infection (2.8) procedures before incubation.
• Constant weight (W) is used for further calculations like weight loss or moisture content.

flowchart TD
    A[Test Blocks + Feeder Blocks] --> B[Place in Bottles]
    B --> C[Incubate at 25±1°C, 70±4% RH for 12 weeks]
    C --> D[Remove & Clean Mycelium]
    D --> E{Moisture Determination?}
    E -- Yes --> F[Weigh Immediately]
    E -- No --> G[Dry in warm air]
    G --> H[Condition at 30°C, 70±4% RH]
    H --> I[Weigh to Constant Weight (W)]

This ensures consistent fungal exposure and reliable durability testing as per IS 4873 Part 1.

IS 4873 Part 1: Calculation of Mass Loss

Key Formulas:

1. Mass Loss (%)
   [ \text{Mass loss, %} = \frac{W_3 - W_4}{W_3} \times 100 ]

   • ( W_3 ) = Conditioned mass before test (g)
   • ( W_4 ) = Conditioned mass after test (g)

2. Retention Value (g/cm³)
   [ R = \frac{G \times C}{100 \times V} ]

   • ( G = W_2 - W_1 ) = mass of solution absorbed (g)
   • ( C ) = preservative concentration in solution (g/100 g)
   • ( V ) = volume of block (cm³)
   • ( W_1 ) = conditioned mass before treatment (g)
   • ( W_2 ) = mass immediately after treatment (g)

Treatment & Conditioning Summary:

• Blocks are vacuum-treated with preservative (60 mm Hg for 30 min).
• After treatment, wiped and weighed ( W_2 ).
• Conditioned at 30°C, 70 ± 4% RH to constant mass ( W_3 ).
• Mass loss evaluated from ( W_3 ) and ( W_4 ) (post-test mass).

Quick Reference Table:

flowchart

Here are the key formulas and specifications from IS 4873 Part 1 (2008) for Calculation of Retention Value and related parameters:

1. Retention Value (R) Calculation

Retention (g/cm³) represents the preservative absorbed per unit volume of wood.

[ \boxed{ R = \frac{G \times C \times 100}{V} } ]

Where:

• G = Mass of treating solution absorbed by block = ( W_2 - W ) (g)
• C = Mass of preservative in 100 g of solution (g)
• V = Volume of test block (cm³)

Units can be converted to kg/m³ by multiplying g/cm³ by 1000.

2. Mass Loss Calculation (Clause 2.10 & 3.8)

[ \text{Mass loss %} = \frac{W_3 - W_4}{W_3} \times 100 ]

Where:

• ( W_3 ) = Conditioned mass before test (g)
• ( W_4 ) = Conditioned mass after test (g)

3. Threshold Retention (Clause 2.11)

• Minimum preservative retention (kg/m³) that limits decay-induced weight loss to ≤ 5%.
• Determined experimentally by plotting % mass loss vs. retention.

Summary Table:

If needed, I can provide a flow diagram for

IS 4873 Part 1: Threshold Retention Summary

Definition:

• Threshold Retention: Minimum preservative amount (kg/m³ wood) preventing decay by a test fungus.
• Determined where weight loss ≤ 5% after fungal exposure.

Key Formula (Clause 2.5):

[ \text{Retention (R)} = \frac{G \times C \times 100}{V} \quad \text{(g/cm}^3\text{)} ]

Where:

• (G = W_2 - W) = mass of preservative solution absorbed (g)
• (C) = % preservative in solution (g/100g)
• (V) = volume of wood block (cm³)

Convert g/cm³ to kg/m³ by multiplying by 1000.

Test Method (Clause 2.11 & 3):

• Wood blocks impregnated with varying preservative concentrations.
• Conditioned at 30°C, 70±4% RH to constant mass.
• Exposed to fungi; weight loss measured.
• Threshold retention = minimum preservative preventing >5% decay.

Table Reference:

• Clause 3.9 contains threshold retention values for different preservatives and fungi (refer IS 4873 Part 1 for exact values).

Summary Diagram:

flowchart TD
    A[Wood Blocks] --> B[Impregnate with preservative solutions]
    B --> C[Condition at 30°C, 70±4% RH]
    C --> D[Expose to test fungi]
    D --> E[Measure weight loss]
    E --> F{Weight loss ≤ 5%?}
    F -- Yes --> G[Threshold retention achieved]
    F -- No --> H[Increase preservative concentration]

Use IS 4873 Part 1 for detailed threshold retention tables and specific preservative-fungus combinations.

IS 4873 Part 1: Conditioning of Test Blocks

Key Specifications & Procedure (Clauses 3.2 & 2.2.2)

• Drying: Oven dry blocks at 100°C to 105°C to constant mass (W).
• Sample Size: 12 blocks per preservative concentration.
• Leaching Start:
  • Oil-type preservatives: after 3 days
  • Water-borne preservatives: after 14 days
• Leaching Exposure:
  • 6 blocks: 14 days at 50°C, except 2 hours at room temp for the first 9 days.
  • 6 blocks: No leaching.
• Conditioning: Both leached and unleached blocks conditioned at:
  30°C and 70 ± 4% RH

Incubation (Clause 2.9)

• Incubate blocks in bottles at 25 ± 1°C, 70 ± 4% RH for 12 weeks.
• After incubation, clean, dry, and condition blocks again at 30°C and 70 ± 4% RH to constant weight.

Mass Loss Calculation (Clause 2.10)

[ \text{Mass loss, %} = \frac{W_3 - W_4}{W_3} \times 100 ]

• (W_3) = Conditioned mass before test
• (W_4) = Conditioned mass after test

Summary Table

flowchart TD
    A[Drying at 100-105°C] --> B[Leaching Start]
    B --> C{Preservative Type}
    C -->|Oil

IS 4873 Part 1: Use of Tolerant Fungi in Wood Preservative Testing

Key Points from Clauses 2.7.1 to 3.4:

• Purpose: Tolerant fungi are essential in testing preservatives to ensure efficacy against resistant wood-rotting fungi.
• Selection Criteria (2.7.1):
  • Fungi must be resistant to antiseptics.
  • They should grow quickly and cause rapid weight loss in test timber.

Specified Tolerant Fungi (2.7.1.1):

Testing Guidelines:

• Include these tolerant fungi always when testing preservatives (2.7.2).
• Other important wood-rotting fungi may be substituted for special investigations.
• Use the same fungi as per clause 2.7.1 for all preservative tests (3.4).

Summary Table for Quick Reference:

This ensures preservatives are tested against fungi that realistically challenge their protective capability.

IS 4873 Part 1: Data Reporting and Rounding Off

• Rounding Off Rule (IS 2:1960):
  Final test or analysis values must be rounded off following IS 2:1960.

  • Retain the same number of significant figures as the specified value in the standard.
  • This ensures consistency and clarity in reporting.

• Calculation of Mass Loss (Clause 3.8):
  Follow the procedure outlined in Clause 2.10 (not provided here), typically involving:
  [ \text{Mass Loss (%)} = \frac{\text{Initial Mass} - \text{Final Mass}}{\text{Initial Mass}} \times 100 ]

Summary Table for Rounding Off (IS 2:1960)

Key Points:

• Always match the precision of the reported value to the standard's specified precision.
• Use the mass loss formula to calculate corrosion or material loss in testing.
• Refer to IS 2:1960 for detailed rounding rules.

flowchart TD
    A[Test/Analysis Result] --> B{Number of Significant Figures}
    B -->|Match Specified Value| C[Round Off as per IS 2:1960]
    C --> D[Report Final Value]

This ensures standardized and reliable reporting in compliance with IS 4873 Part 1.