ProECO Organic Cotton Interlock: The Complete Guide to Wazoodle's Smooth Organic Cotton Fabric

What ProECO Organic Cotton Interlock Is and Why It Matters

ProECO Organic Cotton Interlock is a double-knit fabric made from 100% certified organic cotton, manufactured by AKAS Tex as part of the ProECO sustainable fabric collection. The interlock construction creates identical smooth surfaces on both sides with flat, stable edges that don't curl — a fundamental difference from the brushed pile of ProECO Organic Cotton Fleece and the loop-backed construction of ProECO Organic Cotton French Terry. This makes interlock the most beginner-friendly knit in the ProECO collection and the thinnest at 0.028" — designed for next-to-skin garments rather than absorbent cores.

The family includes four variants at 200–215 GSM with Standard, FoodSAFE (FDA-certified food contact), Silver (antimicrobial odor control), and Print (decorative patterns) options. ProECO SustainSafe (chemical-free manufacturing) processing ensures every variant arrives free from manufacturing residues, while 30% crosswise stretch provides comfortable garment fit without spandex content. All variants hold CPSIA certification, UPF 50+ sun protection, Class 1 flammability (general apparel including children's sleepwear), and Forever Chemicals-Free verification. Made in USA with US Cotton Trust Protocol verified organic cotton.

Multiple customers describe the post-wash texture as "like butter" and note that quality 100% cotton interlock is "hard to find" — this fabric fills a genuine market gap. First-time knit sewers report successful projects thanks to the stable, forgiving construction.
For how ProECO SustainSafe technology works, see "What is ProECO SustainSafe Technology?"

The Complete ProECO Organic Cotton Interlock Lineup

ProECO Organic Cotton Interlock includes four variants sharing the same double-knit interlock construction and smooth-both-sides surface. All provide 30% crosswise stretch, flat non-curling edges, and Ready-AbZORB (immediate absorbency) processing. Your decision is treatment type — whether you need the standard base, FDA food-contact certification, antimicrobial odor control, or decorative prints.

Standard and Print Variants — 215 GSM

W-420 ProECO Organic Cotton Interlock: The foundation variant. 215 GSM, 60–64" width, 0.028" thick, 30% crosswise / 10% lengthwise stretch, 3–4% width / 7–8% length shrinkage. Available in multiple solid colors including dusty blue and black. The go-to for t-shirts, baby clothing, leggings, pajamas, and casual wear.
W-604 ProECO Organic Cotton Interlock Print: Same 215 GSM base with surface-applied decorative patterns. Print patterns may add 1–5% weight and require 20–40% additional yardage for pattern matching. For children's apparel, cloth diaper outer shells, baby accessories, and craft projects where visual appeal matters.

Silver Variant — 215 GSM

W-559 ProECO Organic Cotton Interlock Silver: Same 215 GSM base with Silver Plus (antimicrobial odor control) inhibiting 99.9% bacterial growth through 50+ wash cycles with proper care. For baby clothing, cloth diaper inner layers, underwear, intimate apparel, sleepwear, and any application where odor control during extended wear matters.

FoodSAFE Variant — 200 GSM

W-321 ProECO FoodSAFE Organic Cotton Interlock: 200 GSM (slightly lighter than the 215 GSM Standard) with FDA food-contact certification per 21 CFR 177.1680 and 175.300. Tested stable from -20°C to 250°F across acidic and fatty foods. For reusable food storage bags, sandwich wraps, bowl covers, baby bibs, breast milk storage, and coffee filters.

Key Concept: ProECO Organic Cotton Interlock is smooth on BOTH sides with no pile, no loops, and no wrong side — unlike ProECO Fleece (brushed pile) or French Terry (loops on reverse). This eliminates fabric orientation decisions during cutting and makes it the easiest ProECO construction for beginners. Both sides can face outward in the finished product.

All fabric specifications may vary ±10% due to textile industry manufacturing standards.

Choosing Your ProECO Organic Cotton Interlock: Treatment Type

All ProECO Organic Cotton Interlock variants share 100% organic cotton construction, CPSIA certification, double-knit interlock stability, Class 1 flammability, and Ready-AbZORB (immediate absorbency) processing. Your decision is purely about treatment capability — the physical construction is consistent across the family.

When to Choose Each Treatment

Standard (W-420) — Choose for t-shirts, baby clothing, leggings, pajamas, and general garment construction where organic cotton softness and chemical-free processing are sufficient. The most versatile and cost-effective option. Customers describe this as "premium organic 100% cotton interlock at a great price."
FoodSAFE (W-321) — Choose when your product contacts food directly — reusable snack bags, bowl covers, sandwich wraps, breast milk storage, coffee filters. FDA certification (21 CFR 177.1680 and 175.300) is required for commercial food-contact products. Note: 200 GSM, slightly lighter than the 215 GSM Standard.
Silver (W-559) — Choose for extended-wear applications where odor control between washes matters — underwear, intimate apparel, cloth diaper inner layers, baby clothing, sleepwear. A customer with bladder control needs confirmed effective odor resistance in underwear made from this fabric.
Print (W-604) — Choose when decorative patterns matter — children's apparel, cloth diaper outer shells, baby accessories. Same 215 GSM performance as Standard with surface-applied prints. Budget additional yardage for pattern matching.

Silver variants require specific care to maintain antimicrobial effectiveness — never use fabric softeners or chlorine bleach, which permanently destroy the Silver Plus treatment. This care restriction applies to ALL variants for preserving absorbency, but is especially critical for Silver.

For cross-family comparisons between ProECO Organic Cotton Interlock and other ProECO constructions (Fleece, French Terry, Jersey), see the relevant Decision Framework articles.

Working With ProECO Organic Cotton Interlock: Sewing and Construction Guide

ProECO Organic Cotton Interlock is the most beginner-friendly knit in the ProECO collection. Customers consistently describe it as "easy to sew on" and "stable" — the double-knit construction eliminates the edge curling and stretching that makes jersey challenging for new knit sewers. A first-time knit sewer reported feeling confident their project would succeed specifically because of this fabric's forgiving behavior.

Cutting and Layout

Pre-wash in hot water before cutting — expect 7–8% length shrinkage and 3–4% width shrinkage. Fibers compact during washing, creating a slightly heavier hand and improved body that customers describe as "perfect" weight. Test a sample piece first.
Both sides are smooth and identical — difficult to distinguish right from wrong side. Mark your chosen "right side" before cutting. For Print variants, the pattern identifies the face.
Flat, stable edges don't curl during cutting — no weights or pins needed to manage edge roll like jersey requires. Rotary cutter or sharp scissors both work cleanly.
Print variants: Account for 20–40% additional yardage for directional prints and pattern matching.

Sewing Recommendations

Needle: Ballpoint or universal needles — size 80/12 for general construction, 90/14 for multiple layers at seam intersections.
Thread: Polyester thread for durability through repeated hot-water laundering.
Stitch type: Standard straight stitch works for most construction — the 30% crosswise stretch is moderate enough that a narrow zigzag (2mm width) or stretch stitch provides adequate seam flexibility. Serged edges prevent raveling.
Tension: Standard machine tension works without adjustment for most machines — the stable double-knit construction doesn't fight the feed like single-knit jersey does.
Pattern fit: Account for 30% crosswise and 10% lengthwise stretch when selecting pattern sizes — important for leggings and fitted garments where stretch determines comfort.

Pairing ProECO Organic Cotton Interlock With Other Wazoodle Fabrics

ProECO Organic Cotton Interlock is primarily a garment fabric — the smooth, thin construction serves as next-to-skin layers, outer garment shells, and lightweight linings. In multi-layer products, it typically functions as the skin-contact or outer decorative layer rather than the absorbent core.

Layer Partners for Multi-Layer Builds

Absorbent core (below the interlock): ProECO Organic Cotton Fleece or ProECO Organic Cotton French Terry provides the absorbent layer in cloth diapers, menstrual pads, and incontinence products where interlock serves as the smooth skin-contact surface.
Barrier layer (below absorbent core): ProSoft 1 mil ECO-PUL provides waterproof backing for leak-proof products. ProSoft FoodSAFE PUL provides FDA-certified waterproof backing for food storage builds using FoodSAFE interlock.
Absorbent boosting: Zorb Original or Zorb 3D Stay Dry Dimple adds concentrated absorption capacity between interlock and barrier layers.

Proven Layer Stack Configurations

Cloth diaper (fitted): ProECO Organic Cotton Interlock (W-420, skin side) → ProECO Heavy Organic Cotton Fleece (absorbent core) → ProSoft ECO-PUL (barrier). Interlock's smooth surface provides comfortable skin contact while fleece handles absorption.
Reusable menstrual pad: ProECO Organic Cotton Interlock (W-420, skin side) → ProECO Organic Cotton French Terry (absorbent core) → ProSoft ECO-PUL (barrier). The thin 0.028" interlock keeps the skin-contact layer smooth and discreet.
Reusable food storage bag: ProECO FoodSAFE Organic Cotton Interlock (W-321, food-contact lining) → ProSoft FoodSAFE PUL (outer shell). Both layers FDA-certified for food contact.

Your results may vary based on product design and construction.
For complete build guidance on specific projects, see the relevant Application Discovery articles.

Common Applications for ProECO Organic Cotton Interlock

ProECO Organic Cotton Interlock is most commonly used for t-shirts, baby clothing, leggings, intimate apparel, pajamas, and reusable hygiene products. The smooth-both-sides construction and moderate stretch make it the most versatile garment fabric in the ProECO collection.

T-shirts and casual tops — The primary application. Customers report the 215 GSM weight provides structure without cling and full opacity without see-through issues. One customer successfully made long-sleeved t-shirt dresses with v-necklines, describing a "great fit" that holds its shape through wear. Post-wash fibers compact into what users call "perfect" weight.
Baby clothing and children's wear — Bibs, onesies, baby caps, leggings, and everyday children's garments. CPSIA certification and organic cotton composition support commercial children's product sales. Multiple customers specifically choose this fabric for baby items, citing confidence in the organic and chemical-free processing.
Leggings and fitted garments — The 30% crosswise stretch provides comfortable movement while 10% lengthwise stretch maintains garment length. Suitable for leggings, fitted pants, and casual activewear.
Pajamas and sleepwear — Class 1 flammability allows use in children's sleepwear without restriction. The breathable organic cotton construction regulates temperature for comfortable all-night wear.
Menstrual pads and period underwear — Multiple customers use this as the skin-contact layer in reusable menstrual products, valuing the smooth organic surface against sensitive skin. Pairs with absorbent fleece or French terry cores.
Underwear and incontinence products — Silver variant validated by a customer with bladder control needs who confirmed genuine odor resistance during extended wear. Print variant also used for protective underwear and bladder leak pads.
Reusable food products (FoodSAFE variant) — Snack bags, sandwich wraps, bowl covers, breast milk storage, coffee filters, and cloth napkins. FDA certification required for commercial food-contact products.
Summer casual wear and sun wraps — UPF 50+ protection makes this suitable for outdoor garments including casual button-front shirts, pullovers, and sun wraps blocking 98% UV radiation.

For complete build guides for specific applications, see the relevant Application Discovery articles.

ProECO Organic Cotton Interlock Certifications

All ProECO Organic Cotton Interlock variants hold the same core safety certifications through ProECO SustainSafe (chemical-free manufacturing) processing. FoodSAFE adds FDA food-contact certification. These certifications support customers selling handmade products commercially — particularly children's items, food-contact products, and intimate apparel.

Safety Certifications and Chemical-Free Verifications

CPSIA Certified: Children's product safety compliance (lead, phthalates, BPA testing)
Flammability Class 1: Per 16 CFR Part 1610 — general apparel classification suitable for children's garments and sleepwear
California Proposition 65 Compliant
EU REACH SVHC and RoHS 10 Compliant
UPF 50+: Blocks 98% UV radiation
Made in USA: EPA/OSHA manufacturing standards
US Cotton Trust Protocol: Verified sustainable organic cotton sourcing
FDA Food Contact (FoodSAFE W-321 only): Certified per 21 CFR 177.1680 and 175.300 for repeated-use food contact — tested stable from -20°C to 250°F across all food types
Forever Chemicals-Free: No PFAS, PFOS, PFOA, PTFE detected
BPA-Free, Phthalate-Free, Lead-Free: Tested per CPSIA standards
pH 7.4 (Neutral): No acidic or basic residues

Fabric vs. Finished Product: CPSIA certification of the fabric does not automatically certify your finished product. Finished children's products may require independent testing depending on your product category and sales channels.

For what these certifications require and mean for your products, see the relevant Features Discovery articles.

ProECO Organic Cotton Interlock Care

ProECO Organic Cotton Interlock improves with washing — the organic cotton fibers compact and soften, creating the "like butter" texture customers describe and a slightly heavier, more structured hand feel that makes garments drape better than the unwashed fabric suggests.

Washing

Wash hot water with standard detergent. Organic cotton tolerates high temperatures safely, supporting sanitation-level hygiene for baby and food-contact products. Use an extra rinse cycle to prevent detergent buildup, which reduces breathability over time.

Drying

Tumble dry medium heat. Organic cotton tolerates higher temperatures, but medium heat optimizes dimensional stability. Hot iron acceptable when pressing is needed.

What to Avoid

Never use fabric softeners or dryer sheets — they permanently coat fibers, reducing breathability and absorbency. For Silver variants, fabric softeners also permanently destroy antimicrobial effectiveness. Avoid chlorine bleach — it degrades cotton fiber over time. Oxygen bleach is acceptable for all variants.

Pre-Wash Requirements

Pre-wash is essential before cutting — expect 7–8% length shrinkage and 3–4% width shrinkage. Always pre-wash at the temperature you'll use for the finished product, as natural cotton fiber continues to shrink incrementally with repeated laundering. The first wash produces the most significant change.

ProECO Organic Cotton Interlock Specifications

All ProECO Organic Cotton Interlock variants share the same double-knit construction, stretch properties, and shrinkage behavior. The primary differences are treatment type and a slight weight variation on the FoodSAFE variant (200 GSM vs 215 GSM). All share 100% organic cotton fiber, pH 7.4, UPF 50+, Class 1 flammability, and 4.5 color fastness rating.

Variant	Weight	Thickness	Width	Stretch (W × L)	Shrinkage (W × L)	Treatment
W-420	215 GSM	0.028"	60–64"	30% × 10%	3–4% × 7–8%	Standard
W-604	215 GSM	0.028"	60–64"	30% × 10%	3–4% × 7–8%	Print
W-559	215 GSM	0.028"	60–64"	30% × 10%	3–4% × 7–8%	Silver
W-321	200 GSM	0.028"	60–64"	30% × 10%	3–4% × 7–8%	FoodSAFE

All fabric specifications may vary ±10% due to textile industry manufacturing standards.