Recently, a Canadian customer completed its third order with a down payment of 30,000 US dollars. In the four months since the first cooperation, the customer has placed orders three times in a row. That is, after receiving the first batch of glass candle jars, they placed two additional orders in a short period of time. This continuous trust from customers is truly gratifying.
Customer Joris initially got in touch with us via Instagram. He noticed that among our products, there was a glass candle jar with a gilded maple leaf pattern, which precisely met his market demand. In the initial communication, Joris expressed her need for a custom maple leaf pattern and gilding effect. As he might have had a bad experience with the gilding process in the past, he cautiously raised questions about possible quality issues and their solutions at the beginning of the cooperation. Sunny Glassware has been deeply engaged in the industry for over two decades and possesses an experienced quality control team. It can handle various complex issues in the processing of glass candle jars and can ensure that all defective products are effectively identified and resolved before delivery.
I. Analysis of Common Hot Stamping Quality Issues and Their Causes
1. The hot stamping does not adhere firmly and is prone to scratching off
Cause analysis
(1) Insufficient temperature: As glass is a poor conductor of heat, it heats up relatively slowly. Suppose the temperature of the hot stamping head or the heating time is insufficient; in that case, the adhesive layer of the hot stamping foil cannot be fully activated and effectively combined with the glass surface.
(2) Insufficient pressure: Insufficient pressure will result in inadequate contact between the hot stamping foil and the glass surface, affecting the adhesion effect.
(3) Cleanliness of the glass surface: The presence of impurities such as grease, dust, or moisture on the surface will form an isolation layer, significantly affecting adhesion.
(4) Improper selection of hot stamping foil: Hot stamping foil specifically designed for glass or non-absorbent materials was not used. The adhesive for ordinary hot stamping foil is suitable for the paper fiber structure and cannot meet the requirements of the glass surface.
2. Incomplete or mottled patterns (incomplete transfer)
Cause analysis
(1) Uneven pressure on curved surfaces: The glass cup has an arc-shaped curved surface, while the hot stamping head is usually designed flat. If the fixture design is unreasonable, it will lead to uneven pressure distribution and ineffective transfer in some areas.
(2) Poor exhaust: If air cannot be discharged smoothly during the hot stamping process, bubbles may form, resulting in missing patterns.
(3) Aging or inappropriate hardness of the hot stamping head: If the hot stamping head is too hard, it cannot fit the curved surface; if it is too soft or aged, it may cause the pattern to deform and the edges to become blurred.
3. Poor gloss and a foggy white appearance
Cause analysis
(1) Excessive temperature or prolonged time: Over-heating may cause damage to the metal layer or adhesive layer of the hot stamping foil, resulting in loss of luster and a foggy or dull appearance.
(2) Quality issues of the hot stamping head: If the surface of the hot stamping head is uneven or contains impurities, it will affect the luster of the pattern.
4. Insufficient weather resistance and durability
Cause analysis
(1) Poor wear resistance: Even if the initial effect of hot stamping is good, due to the adhesion mainly relying on physical bonding rather than chemical combination, it is prone to fall off during daily use, cleaning (especially dishwasher cleaning), or friction.
(2) Poor chemical resistance: Contact with chemicals such as detergent and alcohol will accelerate the peeling of the gilding layer.
II. Solution
To effectively address the aforementioned issues, strict control should be exercised in three key areas: materials, equipment, and processes.
1. Select special hot stamping foil (key step) :
Heat transfer foils specifically designed for non-absorbent surfaces such as glass, ceramics, or metals should be adopted. Their adhesive layers have been optimized for smooth surfaces and offer stronger adhesion.
2. Surface pretreatment:
(1) Thorough cleaning: Before hot stamping, clean the glass surface with alcohol or a residue-free cleaner to ensure it is dry, free of grease and impurities.
(2) Preheating treatment: In some processes, the glass can be preheated at a low temperature to remove surface moisture and enhance the hot stamping effect.-
3. Precise control of process parameters (multiple tests required) :
(1) Temperature control: Generally, it needs to be higher than the temperature for paper hot stamping (approximately 150°C to 200°C, depending on the foil model), and the optimal temperature should be determined through experiments.
(2) Pressure control: Greater pressure should be applied for curved surface hot stamping to ensure full contact.
(3) Time control: Due to the slow heat conduction of glass, the hot stamping time should be appropriately extended to ensure that the heat is fully transferred.
4. Use professional curved surface hot stamping equipment
For cup products, it is recommended to use a dedicated cup body gilding machine. This equipment is equipped with a hot stamping head and base that match the arc of the cup body, ensuring uniform pressure distribution, which is significantly superior to manual or flat hot stamping equipment.
5. Subsequent protection treatment (key steps) :
After hot stamping is completed, a transparent protective layer (such as UV varnish or PU protective paint) can be sprayed on the surface of the pattern to enhance its anti-friction and anti-chemical performance and extend the service life of the pattern. This process is widely applied in the surface treatment of high-end gift cups.
Facts have proven that after receiving the first batch of glass candle jars, the customer expressed high satisfaction with the quality and appearance of the products, completely eliminating their doubts about the craftsmanship and quality. In less than a week, the customer sent a repeat purchase order. Joris stated that currently, the exterior decoration of its scented candle holders mainly adopts gilding technology. This collaboration with Sunny Glassware has filled it with confidence to try other decoration techniques (such as decals, electroplating, silk-screen printing, etc.) in the future. It will provide more personalized choices for different consumers.
