When a buyer has narrowed an EVA foam inquiry to 38 Shore C or 45 Shore C, the next useful step is a controlled comparison. Both are common hardness directions in Guowei EVA's standard slab discussions. Choosing between them should produce a clear purchasing decision, rather than another request for material that is simply “softer” or “more supportive.”
This article focuses on evaluating the two candidates in a converter's actual component. For the broader meaning of hardness and the information needed to start an inquiry, read the existing general EVA foam hardness selection guide. Here, the question is narrower: what should you compare, record and confirm before approving one of these two Shore C targets?
Start with a Relative Difference, Not an Application Rule
38 Shore C is softer than 45 Shore C on a comparable Shore C measurement basis; 45 Shore C is the firmer direction. That distinction establishes the candidates. It does not establish which one will work better in your design.
The numerical difference is not a percentage difference in cushioning, support or durability. A Shore C reading also does not identify a foam's density, the force needed to compress a finished pad or its service life. Do not convert the difference into a performance claim without relevant measurements.
For a direct purchasing comparison, first state the decision you need to make. Is an existing liner too firm after lamination? Does a packaging insert need a different feel during insertion? Is the development team evaluating two candidates for a particular footwear layer? Define that question before ordering comparison samples.
Build a Sample Comparison That Is Actually Comparable
If the samples differ in thickness, color, product series, density or construction, a preference cannot be attributed confidently to hardness alone. Aim to keep other requirements aligned where feasible, and record any differences that remain. If the supplier cannot provide an otherwise equivalent pair, treat the exercise as a comparison of two materials, not an isolated hardness experiment.
- Label each candidate: identify the sample, supplier, stated Shore C target and any known material differences.
- Prepare the finished thickness: compare stock converted to the thickness your component requires, rather than mismatched pieces.
- Use the same component drawing: align the shape, openings and position within the assembly.
- Apply the same conversion sequence: use the intended cutting, punching or lamination method for both candidates.
- Compare against a reference: include the approved current material or another clearly identified target where available.
- Record the outcome: describe which condition was acceptable, which was not, and any further evaluation needed.
For recorded hardness measurements, use the agreed Shore C instrument and procedure rather than switching scales between samples. ASTM's durometer guidance explains why readings depend on the indenter, force and test conditions. This is measurement background, not a statement that Guowei samples carry a particular test certification.
Sample format, delivery method and related costs should be discussed before ordering. Do not assume a sample labeled by color or series demonstrates the difference between 38 Shore C and 45 Shore C. Confirm what the supplied sample represents and whether it is appropriate for your comparison.
Compare the Candidates in the Finished Construction
| Evaluation point | Question for the 38 Shore C candidate | Question for the 45 Shore C candidate |
|---|---|---|
| Target feel | Does the softer direction match the intended feel? | Does the firmer direction match the intended feel? |
| Finished assembly | Is it acceptable after the intended layers and shaping? | Is it acceptable in the same finished construction? |
| Conversion trial | Does the prepared material meet your processing requirements? | Does it meet those same requirements with comparable preparation? |
| Approval basis | What observations or agreed tests support acceptance? | What observations or agreed tests support acceptance? |
The table is a comparison checklist, not a ranking. A softer candidate may be evaluated for a particular feel, while a firmer candidate may be evaluated where firmness is the design priority. Neither statement promises that the material will meet a finished-product requirement without checking the actual construction.
Footwear material processing
Identify the layer being made and what surrounds it. Compare the candidates at the required thickness with the intended facing or bonded layers. Record the feel in that assembly and the result of your normal component evaluation. A preference based on squeezing an unconverted slab may not represent the selection question for the footwear layer.
The footwear material application page explains the base-material supply context. It does not mean every footwear component should use either 38 Shore C or 45 Shore C. If neither candidate meets the design requirement, reopen the material brief rather than forcing a choice between the two.
Packaging inserts and liners
Use the intended insert geometry and the item being packed. Evaluate fitting, removal and the contact areas in the complete packaging structure. If transport protection matters, use the tests appropriate to the packaged product and distribution conditions. A Shore C preference from handling a sample is not a substitute for packaging validation.
A 45 Shore C candidate is not automatically more protective, and a 38 Shore C candidate is not automatically better for a delicate item. Both can be evaluated against the same design brief. Consult the packaging application guidance for the product information that should accompany the material discussion.
Other liners, sports padding and industrial cushioning
Describe where the foam sits, how it is attached and what must be evaluated in use. For a bag liner, that may include its feel with a facing material. For a pad or industrial cushion, define the relevant finished-part requirements separately. The final choice depends on thickness, structure and use conditions, not a universal assignment of one hardness to an industry.
Separate Hardness Selection from Stock Preparation
Guowei EVA supplies compression-molded EVA foam sheets and slabs as base material for downstream processing. The standard slab reference is 3000 × 1500 × 60 mm, with black and white as the main standard colors. Your comparison should distinguish this incoming format from the thinner or shaped stock used in the trial.
Specify who will perform thickness splitting or skiving, who will cut the samples and whether lamination is included in the evaluation. Length and width cutting does not itself reduce thickness. The large-format EVA slab guide covers the stock planning details so the hardness comparison can remain focused on the material decision.
Requirements within 25–65 Shore C can also be discussed, subject to confirmation of the order. This does not imply all hardness, color and size combinations are in stock. A sample approval should be followed by confirmation of the actual production specification and supply scope.
Turn the Trial Result into an Order Reference
“We prefer the firmer sample” is useful feedback, but an order needs an identifiable reference. Keep the sample label, intended Shore C target, finished thickness, color and component drawing together. Record any differences between the trial preparation and the planned production process.
Also distinguish a subjective preference from a measurable acceptance requirement. If hardness or another property is an incoming acceptance criterion, agree its method and acceptable limits before ordering. This guide supplies no fixed tolerance. If the decision rests on an approved sample, identify how that sample will be retained and referred to in later discussions.
Send the chosen reference with the order quantity, destination and processing responsibilities. If the trial is inconclusive, explain why: for example, both candidates may require further evaluation after lamination. That is more actionable than changing the hardness target without explaining the unresolved design issue.
Frequently Asked Questions
Does the difference between 38 and 45 Shore C give a cushioning percentage?
No. The values are hardness readings on the stated scale, not percentages of impact absorption or cushioning. Such performance requires evaluation relevant to the complete component and its use conditions.
Can I compare an unsplit 38 Shore C slab with a thin 45 Shore C sheet?
You can observe the two pieces, but that does not isolate the hardness difference. Prepare comparable finished thicknesses and constructions, or record the comparison as involving multiple material and geometry differences.
How should I document a preference found after lamination?
Identify the foam sample, facing layers, finished thickness and conversion sequence. Record the observed result in the assembly so the supplier understands the approval basis, rather than receiving only a hardness number.
What if neither candidate meets the component requirements?
Return to the application brief and identify the unmet requirement. Other hardness directions can be discussed subject to confirmation, but thickness, structure or processing may also need reconsideration. Do not assume hardness is the only variable to change.
Does approving a sample establish availability for a bulk order?
No. Confirm the selected specification, color, quantity and supply arrangements separately. Sample evaluation establishes a material direction; it does not promise stock availability or a fixed delivery schedule.
Make the Choice Traceable
A useful 38 versus 45 Shore C comparison ends with an identified sample and a documented component result. Discuss a two-hardness sample comparison with Guowei EVA using your reference material, application, finished thickness, processing method and target feel. These details support a purchasing decision that can be communicated consistently from development through the order.