Soft Wash Mix Ratio Guide
A soft wash ratio needs three labels: what the parts represent, where the mix is measured and the strength of the SH source. Without those details, “4:1” is incomplete.
Read the ratio convention first
WashCalculator writes a water-to-SH-source ratio as water:SH. A 4:1 ratio contains four water parts and one SH-source part, making five total parts. The SH source occupies 1 ÷ 5 = 20% of the batch.
| Water:SH source | SH-source share | Final batch from 12.5% source |
|---|---|---|
| 1:1 | 50% | 6.25% |
| 2:1 | 33.33% | 4.1667% |
| 3:1 | 25% | 3.125% |
| 4:1 | 20% | 2.5% |
| 10:1 | 9.09% | 1.1364% |
These are mathematical concentrations, not surface recommendations. A different source strength produces a different final percentage at the same ratio.
Final SH = source SH × SH parts ÷ (water parts + SH parts).
Tank, pickup and outlet are different places
- Batch tank: SH source and water are mixed to the concentration held in the tank.
- Pickup container: the solution available to an injector. It may be straight source or a premix.
- Outlet or surface: the concentration after the equipment adds water or combines streams.
A 2% batch in a tank is not a 2% outlet if a downstream injector dilutes it again. Enter the pickup-container concentration and the measured water-to-solution ratio in the downstream calculator.
Worked example
A 4:1 water-to-SH-source batch using 12.5% source has five total parts. The source fraction is 1 ÷ 5 = 0.20. The nominal batch strength is 12.5% × 0.20 = 2.5%.
For a 20 L final batch, each part is 4 L. Use 4 L of the 12.5% source and 16 L of water before accounting for any compatible additive that belongs inside the final batch volume.
Choose the tool by the question
- Use the SH Dilution Calculator when you know source strength, target batch strength and final batch size.
- Use the Downstream Injector Calculator when you know pickup strength and a measured draw ratio.
- Use the X-Jet and Proportioning Calculator for a configurable two-stream proportion.
The calculators do not select a treatment for siding, roofing, concrete or another surface. Follow the product label, SDS, equipment instructions and applicable rules. Never mix SH with acids, ammonia or incompatible chemicals.