Brown Kraft Envelopes: All Sizes, 28lb Construction and When Kraft Is the Right Choice

Brown kraft envelopes exist because standard white wove envelopes fail under certain conditions. Aggressive postal handling tears corners on thin white stock. Thick document packets push through white wove seams. Interoffice routing cycles put repeated handling stress on envelopes designed for single-use mailing. The brown kraft construction addresses all three failure modes through heavier paper weight, different fiber composition, and in the clasp format a metal closure that handles dozens of open-reseal cycles without adhesive failure.

This guide covers all the brown kraft envelope formats in our catalog: what 28 lb kraft actually means compared to 24 lb white wove, every size from #11 to 10x15, the clasp format and why it exists, coin envelopes in brown kraft, when kraft is the operationally correct choice, when white is still better, and the one printing consideration that trips up kraft first-timers.

What 28 lb Brown Kraft Actually Means

The "28 lb" specification on brown kraft envelopes refers to the bond basis weight: 500 sheets of the base paper at 17 x 22 inches weigh 28 pounds. In GSM terms, 28 lb bond is approximately 104 GSM. Standard office copier paper is typically 20 lb bond (75 GSM). Standard white business envelope stock is typically 24 lb bond (90 GSM). Our brown kraft envelopes are 28 lb (104 GSM), which is approximately 15% heavier per unit area than standard business envelope stock and approximately 38% heavier than copier paper.

The practical consequence of 28 lb vs 24 lb construction: more resistance to tearing at corners and seams during postal handling, greater rigidity that helps thick document packets resist the compression that distorts thinner envelopes, and more structural integrity at the metal clasp eyelet where repeated open-reseal cycles put concentrated stress on the paper around the clasp attachment point. For white envelopes, the 28 lb weight is a premium upgrade. For brown kraft envelopes in our catalog, 28 lb is the standard specification it is the correct weight for the document routing and mailing purposes that kraft serves.

Every Brown Kraft Envelope Format We Carry

#11 Brown Kraft, Gummed Flap

4-1/2 x 10-3/8 inches. The #11 in brown kraft is the correct format when you need the extra clearance a #11 provides over a #10 (for thick letter packets, check-plus-letter combinations, or multi-enclosure programs) but want the durability of 28 lb kraft rather than 24 lb white wove. Legal offices and accounting firms that regularly send payment-with-letter packages keep #11 brown kraft as a standard stock item. The gummed flap is compatible with mailing machine inserters. Mails at USPS First-Class letter rate. See all #11 formats at window envelopes.

6x9 Brown Kraft Clasp, Gummed Flap

6 x 9 inches. The most postage-efficient clasp format. At exactly 6 inches tall, it clears the USPS letter-rate maximum height of 6-1/8 inches light contents qualify for First-Class letter postage ($0.78) rather than flat rate ($1.63). Holds an 8.5 x 11 sheet folded once horizontally, 5 x 7 photos flat, small booklets, folded brochures, and multi-card document packets. For programs where per-piece postage cost matters at volume, this is the clasp format that keeps postage at letter rate rather than flat rate.

9x12 Brown Kraft Clasp, Gummed Flap

9 x 12 inches. The standard for flat-document mailing in brown kraft. Holds a standard 8.5 x 11 sheet flat with clearance on all sides. Contracts, certificates, real estate disclosures, financial reports, and any correspondence important enough to arrive unfolded. USPS flat rate. The dual closure (metal clasp plus gum flap) allows both secure initial mailing and repeated resealing without a new envelope.

9.5x12.5 Brown Kraft Clasp, Gummed Flap

9-1/2 x 12-1/2 inches. The bridge size between 9x12 and 10x13. Provides additional clearance for letter-size packets that push against the 9x12 walls without the full step to 10x13. For programs where the 9x12 is marginally insufficient but the 10x13 provides more room than needed. Also appropriate when the document set includes a 9x12 rigid backer (a stiff insert to keep contents flat) that barely fits in the 9x12 interior.

10x13 Brown Kraft Clasp, Gummed Flap

10 x 13 inches. Holds legal-size 8.5 x 14 documents flat, accommodates thick multi-page packets, and provides the most practical clearance for multi-component packages including cover sheets, exhibits, and attachments. Law firms, real estate agencies, and accounting practices use 10x13 clasp as their primary routing format for substantial document sets. See full details at clasp envelopes.

10x15 Brown Kraft Clasp, Gummed Flap

10 x 15 inches. Maximum standard size in the brown kraft range. For legal-size multi-page packets that exceed the 10x13 capacity, oversized marketing materials, large-format architectural drawings, and any program requiring the largest standard document mailer before custom packaging. At 15 inches tall, it handles 8.5 x 14 legal documents with substantial clearance and accommodates thick legal filings without seam stress.

#1 Brown Kraft Coin, Gummed Flap

2-1/4 x 3-1/2 inches. Small coin storage and presentation envelope. Used for individual coins, watch parts, small gems, seeds, tiny hardware fasteners, and any small item requiring individual packaging. Brown kraft at this size provides a more durable and opaque storage container than white coin envelopes for items that will be filed, stored in drawers, or handled repeatedly. Not mailable as a standalone piece (below USPS minimum size of 3.5 x 5 inches). See all coin formats at coin envelopes.

The Clasp Mechanism: What It Does That Gum Flap Alone Cannot

The metal clasp is the defining feature of the clasp envelope format. It is a two-pronged metal fastener inserted through a reinforced punched eyelet in the envelope flap. To open: bend the prongs back. To close: fold the prongs forward over the flap. The closure is secure enough to survive postal handling without additional tape, and it reseals reliably through 20 or more open-close cycles before the metal shows fatigue at the bend.

The gum flap is the secondary closure used for outbound mailing. When sending via USPS, moisten the gum flap and seal it over the clasp. This provides a sealed, tamper-evident appearance for the postal journey. The recipient breaks the gum seal to access the clasp, then can use the clasp alone for subsequent routing and filing.

No envelope with only a gum flap can be opened and resealed reliably. Once the gum bond is broken, the flap either loses adhesive or must be taped closed. The clasp is specifically what makes the format practical for document packets that cycle through multiple hands before final filing a use case that standard gum-only envelopes cannot serve without replacement at each station.

When to Choose Brown Kraft Over White

Situation	Brown Kraft	White Wove
Document routing multiple department stops	Yes clasp reseals; 28 lb handles handling cycles	Not ideal gum seal is single-use
Thick document packets (5+ pages)	Yes 28 lb resists seam distortion	Adequate for lighter loads; shows stress on heavy
Legal documents mailed flat	Yes 10x13 clasp is the professional standard	Adequate in 9x12 for single sheets, not for thick filings
Standard single-sheet business correspondence	No more expensive and darker background	Yes #10 white wove is the correct and economical choice
Financial statements and invoices	No white security tint is the professional standard	Yes with security tinting
Direct mail and donation appeals	No colored or starburst envelopes perform better	Colored or starburst, not standard white
Interoffice mail and internal routing	Yes standard in most US organizations	Acceptable but less durable
Storage and filing use (not mailing)	Yes 28 lb kraft is durable for file storage	Adequate but lighter weight

Printing on Brown Kraft: What Works and What Fails

Brown kraft creates printing challenges that white envelopes do not. The natural dark brown color of the paper absorbs and alters ink colors. Standard process color (CMYK) printing on brown kraft produces muted, darker results than the same design on white paper because brown subtracts from every color channel. A bright red logo on white becomes a brownish-red on kraft. Yellow disappears almost entirely on natural brown kraft.

What works on brown kraft: single-color black printing (highest contrast, cleanest result), dark single-color printing (navy, dark green, dark red), metallic inks (gold, silver, copper the contrast against the kraft background creates a premium appearance). What does not work: full-color photography, bright or light colors, pastels, yellow, white. For return address and organization name printing on our brown kraft envelopes, black one-color printing produces a clean, professional result. For premium branding with high visual impact, black with a single metallic spot color is the standard for kraft-envelope custom printing programs.

Custom printing with return address and organization name is available on all brown kraft formats through custom printed envelopes.

Why Choose Business Envelopes for Brown Kraft Envelopes

Business Envelopes carries the complete brown kraft range: #1 coin, #11 commercial, and the full clasp series from 6x9 through 10x15. All at 28 lb (104 GSM) brown kraft the correct weight for document routing and flat-mail programs, not the lighter 24 lb substitution common from general supply retailers. Metal clasp with reinforced punched eyelet on all clasp formats. Dual metal prongs rated for repeated open-reseal cycles.

No minimums. Free ground shipping on every order. Same or next business day on blank stock. Custom printing in black and single metallic colors available on all brown kraft formats. Browse all clasp sizes at clasp envelopes and the full catalog including all Tyvek envelopes, 9x12 envelopes, and coin envelopes at all items.

Frequently Asked Questions

What is 28 lb brown kraft?

28 lb refers to the bond basis weight: 500 sheets at 17 x 22 inches weigh 28 pounds, equivalent to approximately 104 GSM. Standard business white envelope stock is typically 24 lb (90 GSM). Our brown kraft envelopes at 28 lb are approximately 15% heavier per unit area than standard business envelope stock, providing better tear resistance at corners and seams and greater structural integrity around the clasp eyelet.

What is a clasp envelope and why does it have a metal clasp?

A clasp envelope has a two-pronged metal fastener through a reinforced eyelet in the flap. The clasp opens by bending the prongs back and reseals by folding them forward. Unlike a gum flap (which is single-use), the clasp handles 20 or more open-reseal cycles before showing fatigue. The clasp exists specifically for document packets that route through multiple departments or reviewers before final filing a use case that gum-only envelopes cannot serve.

Can I use brown kraft envelopes for regular business mail?

Brown kraft is functional for business mail but is typically not the default for standard correspondence. For invoices, statements, and professional business letters, white envelopes (especially security tinted for sensitive content) are the professional standard. Brown kraft performs better than white for document routing, flat-document mailing, and thick packets but not for single-sheet correspondence where white is both cheaper and more conventionally appropriate.

Does brown kraft cost more to mail than white?

No. USPS postage is determined by size (letter vs flat) and weight, not by envelope color or material. A 10x13 brown kraft clasp costs the same in postage as a 10x13 white envelope on identical weight contents. The weight difference between 24 lb white and 28 lb kraft adds a small amount to the total piece weight, which is relevant only when contents are near a postage bracket threshold.

Can I print on brown kraft envelopes?

Yes, with important limitations. Brown kraft absorbs and darkens standard CMYK ink. Black single-color printing produces the cleanest result. Metallic inks (gold, silver, copper) create high contrast and a premium appearance against the natural brown. Avoid bright colors, pastels, yellow, and full-color photography they produce muddy or near-invisible results on dark kraft. Return address and logo printing in black is the practical standard for kraft custom printing.

What sizes do brown kraft envelopes come in?

Business Envelopes carries brown kraft envelopes in #1 coin (2-1/4 x 3-1/2 inches), #11 commercial (4-1/2 x 10-3/8 inches), and the full clasp series: 6x9, 9x12, 9.5x12.5, 10x13, and 10x15 inches. All clasp sizes use 28 lb brown kraft with metal clasp and gum flap dual closure.

What is the difference between brown kraft and Tyvek for large document mailings?

Brown kraft is heavier paper (104 GSM) stronger than standard white wove but still paper. It resists tearing better than white in normal handling but can be torn or moisture-damaged under aggressive conditions. Tyvek is DuPont polyethylene fiber genuinely tear-proof, moisture-proof, and lighter at approximately 14 lb. Brown kraft is the correct choice for budget-sensitive programs and interoffice routing that requires resealing. Tyvek is correct when the document must arrive pristine regardless of handling and a permanent peel-and-seal closure is acceptable.