Your Leading Secrets & Envelopes Supplier
Xiamen Blue City Print Co., Ltd. is a professional paper craft manufacturer since 1995, located in Xiamen and have our own factory focusing on providing personalized and efficient solutions.We have closely collaborated with numerous customers across different countries, understanding various customer needs and the dynamic changes in the market. It realized that being responsive to market demands and offering diverse solutions are key to gaining customer trust in the printing industry.
Why Choose Us
Complete qualifications
Successfully passing BSCI audit and FSC certification, our products meet global toy safety standards.
One Stop Solution
Our team of dedicated professionals can answer your questions about game making and help you navigate every step of the manufacturing process, meanwhile my team well-equipped to handle various challenges and provide a one-stop purchasing solution for the clients.
Advanced equipment
Our factory is equippedl with professional Spheroidizing furnace, including Heideberg printing machine, Auto cutting machine, Auto foil machine, Laminating machine, Box forming machine, Card making machine etc, to meet production needs.
Types of Secrets & Envelopes




Business envelopes
Business envelopes are commonly used for professional communications such as sending letters, invoices, contracts, and other business documents. They are available in various sizes, and most can be customized with logos, return addresses, and branding.
Check envelopes
Check envelopes are designed to securely hold checks or payroll documentation and help ensure safe and discreet delivery. With opaque materials and secure closures, they protect sensitive financial information from being viewed during transit.
Form envelopes
Form envelopes are specialized envelopes designed for sending legal forms, tax documents, medical records, and other important business documents. They are typically larger than standard envelopes to accommodate multi-page forms without folding. Featuring single or double window openings for easy address visibility and security tints to protect contents, form envelopes help ensure that documents remain intact and confidential during transit.
Shipping envelopes
Shipping mailers and envelopes are durable, lightweight packages used to send documents, small items, or sensitive materials. Most are made from stronger, more durable material types to help ensure safe and intact delivery.
Single vs. Double windows vs. No windows
Single window envelopes have one transparent window, typically for displaying the recipient's address, making them ideal for simple correspondence.
Double window envelopes feature two windows, commonly for the recipient's address and the return address, streamlining bulk mail.
Envelopes with no windows offer no transparency to any contents inside, adding a level of security and privacy. However, they require addresses to be printed directly on the envelope.
Gummed and self-seal envelopes
Gummed envelopes require moistening to seal, offering a secure closure but taking extra time to seal.
Self-sealed envelopes feature adhesive strips that activate when pressed, making them quicker and more convenient to use.
Confidential vs non-confidential envelopes
Confidential envelopes generally refers to envelopes designed to protect the privacy or sensitive nature of the contents inside the envelope with security features such as security tint or tamper-evident seals. They are commonly used for mailing checks, invoices or statements, contracts, or other correspondence that require privacy and security.
Nonconfidential envelopes typically are standard mail envelopes without security features. They are used typically for everyday mail or correspondence where confidentiallity is not a concern.
Applications of Secrets & Envelopes
Corporate team building
Create collaborative puzzle challenges, hidden mission systems, and interactive problem-solving activities for company events an
Scavenger hunts
Guide players through location-based clue progression using sealed instructions, hidden coordinates, and sequential puzzle reveals.
Subscription mystery boxes
Enhance monthly mystery experiences with confidential documents, hidden evidence packs, and progressive story content.
Interactive mail games
Deliver immersive at-home detective experiences through mailed clue envelopes and serialized investigations.
Puzzle competitions
Use timed clue reveals, challenge stages, and locked progression systems for live or online puzzle tournaments.
Historical reenactments
Present classified wartime documents, secret orders, and immersive historical evidence for educational or entertainment events.
Museum experiences
Transform exhibitions into interactive discovery journeys using hidden clues, artifact reveals, and narrative exploration mechanics.
Educational escape kits
Build classroom-friendly puzzle systems that encourage critical thinking, teamwork, and hands-on learning.
Detective-themed parties
Create immersive party experiences with suspect files, hidden motives, secret evidence, and interactive case-solving mechanics.
Treasure hunts
Reveal maps, riddles, and hidden objectives gradually to increase suspense and player engagement.
Convention & event experiences
Use interactive envelopes for fan events, promotional scavenger hunts, or immersive convention activities.
Alternate reality marketing campaigns
Brands can use physical reveal systems to create viral mystery experiences tied to product launches or entertainment promotions.
Interactive theater
Allow audience members to uncover hidden storylines, secret character information, and branching narratives during performances.
Wedding & party games
Add mystery games, hidden challenges, or reveal mechanics to weddings, birthdays, and private events.
Classroom roleplay activities
Teachers can create immersive simulations involving historical investigations, science mysteries, or collaborative storytelling.
Our Service
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Size Options |
A4 / A5 Custom Dimensions |
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Recommended gsm |
105gsm, 120gsm, 128gsm, 157gsm, 160gsm , 200gsm, 250gsm / Customizable |
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Common Processes |
lamination, UV, embossing, debossing bronzing, varnish, foil stamping |
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Package |
Lid and base box, mailer bag, Flip box, Customized |
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Art-word Format |
AI, PDF, CDR, PSD |
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Logo/graphic Design |
Customized |
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MOQ |
500 PCS |
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Lead Time |
Depending on your quantity |
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Brand Name |
Customized/OEM |
FAQ
With abundant experience, we are one of the most professional secrets & envelopes manufacturers in China. Our factory offer high quality printing services for customers around the world. Welcome to contact us for custom service.













