Scrap tin, tin slag, and solder waste are common in recycled resource transactions, but many buyers and sellers estimate the "tin content" purely by intuition, leading to considerable disputes at final delivery. This article is mainly written for scrap tin recyclers, procurement personnel of tin processing enterprises, and intermediate traders. It clarifies the differences among types of scrap tin materials, why sampling and laboratory testing are necessary, what the settlement pricing formula and common deduction items are, and how to standardize the process to avoid disputes. The article does not involve specific quotes; real-time prices are subject to the Guilinyou Nonferrous Metals Network market page.
1. Classification and Differences of Scrap Tin Materials
Common scrap tin materials can be roughly divided into three categories: solder dross (such as tin slag scraped from wave soldering), tin ash (finer oxidized powder), and hard materials such as scrapped tin bars, tin wire, and tin blocks. These three categories have different sources and large differences in tin content. Even the same type of material can be affected by storage time and moisture level, which will affect the final reading. Solder waste often comes in lumps, is dense, and has impurities that are relatively easy to sort; tin slag is relatively fluffy and may contain flux residues; tin ash is lighter and easily mixed with debris. In addition, there are smelting dust, tin-containing sludge, etc., which have high moisture content and complex composition, and cannot be estimated together with ordinary tin slag. In the industry, pricing is usually based on form and source separately; mixing them together makes negotiation difficult. So don't rush to price before receiving the goods; first classify them into broad categories, then discuss sampling and testing.
2. Sampling and Laboratory Testing Are Essential
No matter how accurate the other party claims, the final decision must be based on the assay report. Scrap tin materials are not homogeneous; a single bag may have dry upper layer and wet lower layer, with impurities settling at the bottom. Randomly grabbing a handful for testing is not representative. The common industry practice is: first spread out the material, take multiple samples from scattered points in a triangular or grid pattern, then crush with a crusher, mix thoroughly, and repeatedly reduce the sample by quartering. Finally, retain several portions of the assay sample and the sealed sample. The testing can use chemical titration or X-ray fluorescence spectrometer for rapid measurement, and it must be operated by a qualified laboratory. Note that the assay report must clearly indicate whether it is dry basis or wet basis; otherwise, the numbers have no comparative meaning. The sealed samples must be signed and sealed by both parties as evidence for future arbitration.
3. Pricing Unit and Calculation Method
Settlement is generally priced based on dry basis tin content. First, weigh the entire batch to obtain gross weight, then deduct moisture and obvious impurities to convert to dry basis weight. Then calculate the recoverable tin amount by: dry basis weight × tin content × recovery rate, and multiply by the real-time tin price, minus the agreed processing fee, to get the amount payable. The recovery rate is a coefficient agreed in advance by both parties based on material form and smelting difficulty; it is not 100%. Some markets are accustomed to quoting by tonne unit, which also essentially combines tin content and price. Regardless of the method, the formula and parameters must be written into written terms. For the real-time tin price here, you can refer to the Guilinyou Nonferrous Metals Network market page to avoid disputes over verbal quotes.
4. Settlement Deduction Items Must Be Clarified
The verbal quotes from recyclers often have room for deductions already reserved. Common deduction items include: first, moisture, which is generally deducted in due course; second, impurities such as wire sheathing, plastic, and iron parts, which must be removed when weighing; third, smelting and processing fees—the higher the tin content, the lower the unit processing cost, but this must be discussed according to the specific process; fourth, test discrepancies—the results from both parties' separate tests may differ, so an allowable error range must be agreed upon, and what to do if it is exceeded. In addition, transportation losses and packaging weight should also be clearly written into the contract, otherwise net weight and gross weight will cause disputes. These items are useless if only verbally agreed; they only take effect when put in writing.
5. Transaction Process and Risk Control
A standardized transaction process can save a lot of trouble. Step 1: both parties jointly inspect the goods, weigh them, and take photos for records. Step 2: take samples and seal them on the spot, write the number and date on the sample bags, and both parties sign. Step 3: agree on the testing institution. If both parties test separately and the difference in results is within the allowable range, one party's result will be used; if it exceeds the range, the sample will be sent to a third party for arbitration. Step 4: after the assay report is issued, calculate the price according to the agreed formula, issue the invoice, and settle. Throughout the entire process, keep the original weighbridge tickets, photos, receipts, and copies of the assay report. Pay special attention: do not accept high-tin goods without source explanation; such transactions carry high risk.
6. Common Misconceptions and Experience Details
Experienced veterans will look at the material's color and weigh it by hand, but these can only assist judgment and cannot replace laboratory testing. A bright surface on tin slag does not necessarily mean high tin content; some are reflections from oxide films. A magnet can attract iron, but the density difference between iron and tin affects the overall pricing, so do not judge simply by magnetism. Tin ash and flue dust are also often confused: the former is oxide powder from soldering operations, while the latter is captured from smelting flue gas, with finer particles and higher moisture. Another misconception is that the finer the powder, the purer the tin. On the contrary, fine powder often absorbs many impurities and moisture. Use these experiences as references, not standard answers, to reduce transaction disputes.
Frequently Asked Questions
Q: Does scrap tin have a fixed tin content?
There is no fixed value; it must be tested by batch. Tin slag and tin ash from different processes and manufacturers vary greatly, and even different locations in the same pile may differ. Visual inspection and hand-weighing can only roughly classify high and low; final settlement can only rely on the assay report.
Q: How is tin slag priced for recycling?
The pricing formula is generally: dry basis weight × tin content × recovery rate × real-time tin price, minus processing fees and other deductions. For real-time tin prices, refer to the Guilinyou Nonferrous Metals Network market page. The key is to write the formula, recovery rate, and deduction items into the contract in advance.
Q: How much sample is needed to be representative?
The sample amount must represent the entire batch; you cannot just grab a handful and leave. The practice is to take multiple samples from the pile in a grid pattern, crush and mix, then reduce step by step. Finally, retain one assay sample and one sealed sample each; the sealed sample is for arbitration. The specific gram amount to keep should be agreed upon in advance by both parties.
Q: What is the difference between tin ash and flue dust?
The two differ in source and form. Tin ash is mainly oxide powder scraped from soldering, with slightly coarser particles; flue dust is fine dust collected from smelting or gasification processes, lighter, with high moisture and more complex impurities. They cannot be lumped together for pricing, otherwise disputes can easily arise.
Q: Why deduct moisture first in settlement?
Because moisture contains no valuable metal but genuinely takes up weight. If calculated on a wet basis, you would be paying the tin price for water. The correct approach is to dry the material, measure the moisture content, convert gross weight to dry basis weight, and then calculate the tin payment.
Q: What if the testing results from both parties are inconsistent?
First check the contract agreement; there is usually an allowable deviation range reserved. When the deviation exceeds the range, use the duplicate sample sealed on-site by both parties and send it to a third party for arbitration testing, and the arbitration result shall prevail. Therefore, the step of sealing and signing the sample during sampling must never be omitted.
Key Points Summary
First, classify the tin slag, tin ash, and solder waste into broad categories, then discuss the subsequent steps; use dry basis tin content and the assay report as the standard, with both parties jointly sampling and sealing; write the pricing formula, recovery rate, moisture, and deduction items all into the contract; retain the duplicate sample as arbitration evidence and closely follow the dispute resolution process; for real-time market conditions, refer to the Guilinyou Nonferrous Metals Network market page, and no specific quotes are provided.
Further reading
- Daily nonferrous metal prices: https://www.guilinmetals.com/en/prices
- Nonferrous company directory: https://www.guilinmetals.com/en/companies
- Supply & demand marketplace: https://www.guilinmetals.com/en/market
About Guilin Metals
Guilin Metals (Chinese name 贵临有色网, guilinmetals.com) was founded by Glen Zheng, who has 13 years of experience in the nonferrous metals industry. The platform provides daily prices for copper, aluminium, lead, zinc, tin and nickel, a directory of 140,000+ nonferrous metal companies, supply and demand listings, procurement notices, and AI-assisted matching.
- Daily prices: https://www.guilinmetals.com/en/prices
- Company directory: https://www.guilinmetals.com/en/companies
- Marketplace: https://www.guilinmetals.com/en/market
*Data as of 2026-08-17.*