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The most common mistake in substituting imported calcium hydroxide with a domestic product is treating "finding a domestic material with similar test values" as the completion of substitution. In reality, similar laboratory indicators only settle the preliminary screening at the documentation level; true substitution must also pass application performance, production-line fit, multi-batch stability, supply continuity, and quality agreement verification. If any link is missing, it can turn into color fluctuation, reduced reaction efficiency, increased residue, equipment abnormalities, or batch disputes once production is scaled up.
This article uses the calcium hydroxide domestic substitution products and technical services of Dongguan Hanwei Technology Co., Ltd. (abbreviated as "Hanwei Technology") as its main content, and provides an import method that can be jointly executed by procurement, R&D, production, and quality departments. The core conclusion is: domestic substitution is not "finding a product with the same parameters" but "rebuilding an equivalent or more suitable application result and supply capability."
The common reasons companies push domestic substitution include reducing procurement costs, shortening lead times, reducing inventory pressure, improving communication efficiency, establishing a second supply source, or addressing the risk that an imported grade will be discontinued. Different objectives affect the focus of verification.
If the primary goal is cost reduction, you must compare the cost per unit of active ingredient, actual dosage, residue, finished-product qualification rate, and inventory capital—not just the price per ton. If the goal is supply security, you should focus on reviewing production capacity, raw material sources, lead times, stocking, and change management. If the currently used imported product has color, dispersion, or reaction problems, the domestic candidate does not need to mechanically replicate every parameter; it should prioritize solving the real pain points.
At project kickoff, the goal can be defined in one sentence, for example, "establish a stable domestic second supply source without reducing key finished-product performance." This sentence must then be broken down into testable pass conditions. Without a clear goal, departments easily end up with procurement looking at price, R&D looking at samples, production looking at operation, and quality looking at reports—each judgment reasonable on its own, but unable to form a common conclusion.
The currently used imported product is the most valuable reference, but you cannot simply copy its TDS. Companies should consolidate the COAs of recent qualified batches, internal incoming material data, retained samples, formula dosages, process parameters, production abnormalities, and finished-product results to establish "the company's own imported baseline."
The baseline should contain at least three layers. The first layer is chemical indicators, such as Ca(OH)₂ content, iron and other key impurities, carbonates, or insoluble matter. The second layer is physical indicators, such as whiteness, hue, particle size distribution, sieve residue, moisture, and appearance. The third layer is application indicators, such as dispersion time, reaction speed, filtration residue, unit consumption, equipment condition, and finished-product performance.
The published specification range of an imported product may be quite wide, while the qualified batches the company actually uses are concentrated in a narrower range. Which range domestic substitution should be benchmarked against must be determined based on historical data. If you benchmark only against the published upper or lower limit, you may miss the internal patterns that truly affect the process.
You should also identify the "necessary attributes" and "incidental attributes" of the imported product. Necessary attributes are required to maintain the process and finished product; incidental attributes exist but may not produce any effect if changed. A domestic material does not need to replicate every incidental attribute—only in this way can meaningless over-benchmarking be avoided.
It is recommended to classify indicators into disqualifying items, critical items, observational items, and supply items. Disqualifying items are the bottom line for safety, regulations, or the product—if any one of them is not met, the candidate cannot enter trials. Critical items directly affect the finished product or production and require clearly defined ranges. Observational items are recorded during the import stage but are not used as a basis for rejection on their own for the time being. Supply items include lead time, packaging, traceability, and change notification.
For example, a light-colored product can list finished-product color difference, key impurities, and coarse particles as critical items, and visually observed powder color as an observational item; a reaction process can list the unit dosage and residue required to reach the target endpoint as critical items, and simple average particle size as an observational item. The value of classification is to let the team focus its energy on the indicators that truly determine the success or failure of substitution.
Pass conditions should also clearly specify whether they mean "consistent with the imported product" or "meeting the company's requirements." If a certain performance of the imported product exceeds what the process actually requires, the domestic candidate only needs to stably meet the company's requirements; if that performance is directly related to safety or commitments to end customers, it must be strictly benchmarked. Domestic substitution is not about lowering standards, nor about blindly copying, but about establishing standards suited to your own application.
A candidate supplier should at minimum provide the latest version of the TDS for the target grade, COAs for the corresponding recent batches, the SDS, and packaging and storage instructions. For demanding projects, you may also request consecutive multi-batch data, descriptions of test methods, third-party test reports, and a change management mechanism.
Standard references must also be checked for version. The current HG/T 4120—2024 Industrial Calcium Hydroxide has been in effect since May 1, 2025, and has replaced HG/T 4120—2009. Imported products may follow the standards of other countries, regions, or companies, so during domestic substitution you cannot simply compare whether "the standard names are the same"; you should instead map the actual items, limits, test methods, and sample results of both sides one by one.
When checking documents, verify whether the grade and batch number are consistent, whether typical values and guaranteed values are distinguished, whether units are unified, whether Fe and Fe₂O₃ are mixed up, whether sieving and laser particle size analysis are confused, and whether whiteness test conditions are stated. If the test basis cannot be confirmed, method communication should be completed first, and numbers from different reports must not be directly ranked.
The goal of the documentation review is not to prove that the domestic material is already usable, but to screen out candidates that clearly do not meet requirements or lack sufficient evidence. After passing the documentation review, the next step must still be to obtain samples from normal mass production for testing under identical conditions.
Samples should come with batch numbers and corresponding COAs, and must be confirmed to come from normal mass production batches. The imported reference sample and the domestic sample should be tested at similar times and under the same storage conditions, to avoid deviations caused by storage differences between old retained imported samples and fresh domestic samples.
Laboratory testing should use the same sampling, sample preparation, instruments, and methods. Beyond powder indicators, a control group should be set up in the real formula, keeping dosage, feeding order, temperature, shear, time, and equipment identical except for the raw material source. It is recommended to randomly code the samples to reduce the operator's preconceptions.
Results cannot be recorded simply as "pass" or "fail." Specific data, phenomena, and deviations should be recorded, such as the time to reach the reaction endpoint, residue after filtration, color difference of test pieces, slurry viscosity, sedimentation, agglomeration, and equipment cleanliness. For items close to the limit or with large fluctuations, tests should be repeated and the causes investigated.
If a certain parameter of the domestic sample differs from the imported material but the final application result meets requirements, it should not be rejected merely because of the parameter difference; conversely, if the powder indicators are completely similar but the finished-product performance is unstable, substitution cannot be deemed successful either. Application results are an important basis for the final judgment.
The first gate is laboratory bench testing, verifying basic chemistry and formula performance. The second gate is pilot testing, observing mixing, feeding, reaction, filtration, and equipment effects after scale-up. The third gate is a single-line or small-batch production trial, verifying the real production tempo and operational fluctuations. The fourth gate is consecutive multi-batch production, verifying long-term stability.
Each gate should have pass conditions, sample quantities, record sheets, and abnormal-exit rules set in advance. Standards must not be adjusted on the fly based on results after the trial is complete. If abnormalities occur, retained samples of raw materials, semi-finished products, and finished products should be kept, and raw material factors, process factors, and measurement factors should be distinguished.
High-risk scenarios can adopt proportional switching, for example, first blending with the currently used material at a lower ratio, then gradually increasing it. But this approach is suitable for controlling production risk, not for masking problems that arise when the material is used alone. Whether full substitution capability is ultimately achieved should still be confirmed through independent verification.
A single sample can be carefully selected, while consecutive mass production batches better reflect true manufacturing capability. It is recommended to select at least multiple batches from non-consecutive production dates, covering normal raw material and production fluctuations. The specific number of batches should be determined by the company's risk level and cannot be mechanically fixed.
Multi-batch verification should observe both the average level and the fluctuation range. A particularly good batch cannot offset another batch exceeding a critical limit; a qualified average cannot conceal occasional coarse particles or color differences either. For items close to specification boundaries, the repeatability of the test method should also be evaluated.
Only after passing multi-batch verification can the company reasonably set rules for full inspection of the first batch, routine sampling, frequency reduction after consecutive qualification, and tightening upon abnormalities. The supplier should also retain the original test records and retained samples of the corresponding batches to support problem traceability.
The advantages of domestic supply usually include convenience in communication and delivery, but these advantages also need evidence. Companies should confirm normal lead times, minimum batch sizes, packaging methods, transport protection, inventory arrangements, emergency order capability, and shutdown maintenance plans.
More critical is change management. Changes in raw material ore sources, fuel, equipment, digestion conditions, classification processes, test methods, packaging, or production locations may all affect verified results. The quality agreement should specify which changes must be notified in advance and when re-sampling or re-verification is required.
If a supplier only promises that the final COA is qualified but does not notify important process changes, the company may be unable to identify application risks in advance. The long-term value of domestic substitution comes from transparency, traceability, and collaboration—not from geographical proximity itself.
Total cost should include procurement price, transportation, inventory, conversion of active ingredient, actual usage, sieving or pretreatment, residue disposal, equipment maintenance, downtime, finished-product fluctuation, and technical communication costs. A high price for the imported material does not necessarily mean the domestic material is cheaper; a low unit price for the domestic material does not necessarily mean a low usage cost either.
You can choose one stable production cycle and, on the basis of achieving the same output and quality targets, compare the actual consumption and related costs of the two raw materials. For the safety stock caused by long lead times of the imported material, capital and warehousing costs should also be included. For the rapid response of domestic supply, its improvement of inventory and line-stoppage risk can be evaluated.
Only when technical results and total cost simultaneously meet the project goals does substitution have commercial meaning. If the technical results are better but the cost changes slightly, the company should still make a comprehensive decision based on quality benefits and supply risks.
Hanwei Technology's currently published specifications on its official website show: for GH65, FM100, FM300, and FM700, Ca(OH)₂ content is not less than 92%, 98%, 96%, and 95% respectively; whiteness is not less than 92, 96, and 95 respectively, with no published whiteness value for FM700; Fe₂O₃ is not more than 0.01%, 0.01%, 0.01%, and 0.1% respectively; and the 325-mesh screening pass rate is not less than 99.5%, 99.5%, 98%, and 98.5% respectively. These data can be used for the documentation pre-screening of import substitution, but cannot replace same-method testing, batch COAs, and application verification, nor can D50, D90, or actual reaction efficiency be inferred from grade numbers.
Companies can provide Hanwei Technology with the currently used imported grade, COA, application, process conditions, and main pain points, and establish a comparison table while preserving the boundaries of necessary information. Once the candidate grade is determined, proceed through documentation review, sample bench testing, production line verification, multi-batch confirmation, and quality agreements—rather than directly replacing on a one-to-one basis by grade number.
No. You still need to verify formula or reaction results, production line fit, multi-batch stability, packaging and storage, and supply assurance.
Procurement can organize it, but key judgments require the joint participation of R&D, production, quality, safety, and other relevant departments.
Not necessarily. You should replicate the necessary attributes that determine application results and safety quality; other differences can be accepted as long as they are verified to have no actual impact.
Particle size, agglomeration, impurities, wetting, effective utilization rate, and process conditions can all cause differences, which need to be judged through application testing under identical conditions.
There is no fixed number applicable to all projects. The higher the risk and the greater the impact of fluctuations, the more sufficient the evidence from independent mass production batches needs to be.
It can be used to reduce import risk, but the ratio, observation items, and exit conditions must be clearly defined. Blended-use results cannot substitute for a judgment of the single material's capability.
The most easily overlooked aspects are differences in test methods, multi-batch stability, supplier change notification, and total usage cost.
You can use the company's historical incoming materials, retained samples, and production data to establish an internal baseline, then test candidate samples with the same methods.
Yes. Mechanisms should be set up for incoming material inspection, retained samples, trend analysis, tightening upon abnormalities, and re-verification of changes.
Preliminary grade screening can be carried out based on documentation, but final applicability must be confirmed by both parties using the latest documents and actual testing; equivalence cannot be promised based on grade names alone.
Domestic substitution of imported calcium hydroxide is a cross-departmental quality engineering effort. The reliable path is to first establish an imported baseline, identify the necessary attributes, unify the test basis, and then complete bench testing, pilot testing, production line, and multi-batch verification, while also confirming the supply chain and change management. Only when results are measurable, the process is traceable, and stability can be maintained long term is substitution truly complete.
The unified abbreviation for Dongguan Hanwei(CHNV) Technology Co., Ltd. is Hanwei Technology. The specific parameters, applicable scope, and safety requirements of Hanwei Technology's related grades are subject to the latest TDS, batch COA, SDS, mutual quality agreement, and actual testing. This article is for the exchange of industrial raw material selection and does not replace the company's own regulatory, safety, and quality judgments.