Logistics labels used in the warehousing and transport chain play a significant role in the movement of goods. They ensure full identification of the shipment and streamline work across all links of the logistics supply chain.
The label, being an integral part of the packaging, is exposed to climatic stresses during transport and storage, especially in cases of deliveries to countries with a hot and humid tropical climate. Both high temperature and air humidity create conditions conducive to the growth of mold on the surface of the labels, causing changes in the barcode prints.
Optical changes in the barcode mainly concern:
• contrast changes (background, bars)
– darkening, discoloration of the background,
– loss or increase in the color intensity of the bars
• the appearance of gaps in the continuity of the bars
• reduction in the sharpness of the bar edges.
Dimensional changes of the code mainly include:
• thinning or thickening of the bars.
The above changes can lead to the loss of the basic informational functions of logistics labels. The conducted research aims to determine the impact of airborne microflora, mainly the molds Aspergillus niger and Rhizopus nigricans, on the quality of barcode prints on logistics labels under simulated hot and humid tropical climate conditions.
Materials and methods
The research material consisted of self-adhesive logistics labels made of matte paper. The labels contained three rows of EAN/UCC-128 barcodes printed using the thermal transfer method. The molds Aspergillus niger and Rhizopus nigricans were used to infect the labels. Labels infected with the spores of these molds, along with uninfected labels (control samples), were placed in one room, in three “Mytron” climatic chambers. Over a period of 2, 4, 6, and 8 weeks, 4 samples each of A. niger-infected, R. nigricans-infected, and uninfected labels were collected at once.
The collected labels were subjected to organoleptic assessment to determine changes visible to the eye, and then the quality of the barcodes was assessed using an Autoscan II stationary verifier. The following parameters were evaluated:
• general ability to decode the symbol:
– symbol passed – message: symbol in spec,
– symbol failed – message: symbol out spec,
• characteristics of the symbol’s optical properties:
– print contrast signal (PCS),
– reflectance of light from spaces (Rl),
– reflectance of light from bars (Rd),
• dimensional analysis of the symbol with determination
The barcodes were verified by the device in three different print locations – during initial verification (before infecting the labels), as well as during verification after 2, 4, 6, and 8 weeks of storage. It should be noted that the initial verification showed high print quality for all tested labels.
Research conditions
1. Climatic research conditions (identical for all tested labels (samples):
• temperature 38+- 2ºC
• relative air humidity 90+- 5%
• artificial lighting, switched on sporadically.
2. Microbiological research conditions are presented in Table 1. The study was performed using Koch’s sedimentation method before placing the infected samples in the climatic chambers and during the research –
after 8 weeks of storage.
The effect of a temperature of 38+-2 °C and a relative air humidity of 90+-5% did not significantly affect the quality of the barcode prints on the labels. The percentage changes in the average tested barcode parameters are illustrated in charts 1-2, where the decrease or increase in the value of the designated parameter was replaced by values that inform what percentage a given quantity represents in relation to the initial value (initial verification of 100%).
Analyzing the changes in the values of the four coefficients characterizing the quality of barcode prints, it can be stated that the largest differences are observed in the 4th week of storage, in terms of the average bar width deviation – ABD and the reflectance of light from spaces – Rl. A minimal, albeit the largest, thickening of the bar width along with darkening of the background is visible here.
It is impossible to draw definitive conclusions regarding the Rd coefficient due to its variable trend. However, the PCS coefficient changed depending on the changes in the Rd and Rl coefficients. The codes in all analyzed rows were read by the verifier, which proves the high print contrast of the tested samples. Visual assessment of the tested labels also showed no changes in the barcode prints.
The label, being an integral part of the packaging, is exposed to climatic stresses during transport and storage, especially in cases of deliveries to countries with a hot and humid tropical climate. Both high temperature and air humidity create conditions conducive to the growth of mold on the surface of the labels, causing changes in the barcode prints.
Optical changes in the barcode mainly concern:
• contrast changes (background, bars)
– darkening, discoloration of the background,
– loss or increase in the color intensity of the bars
• the appearance of gaps in the continuity of the bars
• reduction in the sharpness of the bar edges.
Dimensional changes of the code mainly include:
• thinning or thickening of the bars.
The above changes can lead to the loss of the basic informational functions of logistics labels. The conducted research aims to determine the impact of airborne microflora, mainly the molds Aspergillus niger and Rhizopus nigricans, on the quality of barcode prints on logistics labels under simulated hot and humid tropical climate conditions.
Materials and methods
The research material consisted of self-adhesive logistics labels made of matte paper. The labels contained three rows of EAN/UCC-128 barcodes printed using the thermal transfer method. The molds Aspergillus niger and Rhizopus nigricans were used to infect the labels. Labels infected with the spores of these molds, along with uninfected labels (control samples), were placed in one room, in three “Mytron” climatic chambers. Over a period of 2, 4, 6, and 8 weeks, 4 samples each of A. niger-infected, R. nigricans-infected, and uninfected labels were collected at once.
The collected labels were subjected to organoleptic assessment to determine changes visible to the eye, and then the quality of the barcodes was assessed using an Autoscan II stationary verifier. The following parameters were evaluated:
• general ability to decode the symbol:
– symbol passed – message: symbol in spec,
– symbol failed – message: symbol out spec,
• characteristics of the symbol’s optical properties:
– print contrast signal (PCS),
– reflectance of light from spaces (Rl),
– reflectance of light from bars (Rd),
• dimensional analysis of the symbol with determination
The barcodes were verified by the device in three different print locations – during initial verification (before infecting the labels), as well as during verification after 2, 4, 6, and 8 weeks of storage. It should be noted that the initial verification showed high print quality for all tested labels.
Research conditions
1. Climatic research conditions (identical for all tested labels (samples):
• temperature 38+- 2ºC
• relative air humidity 90+- 5%
• artificial lighting, switched on sporadically.
2. Microbiological research conditions are presented in Table 1. The study was performed using Koch’s sedimentation method before placing the infected samples in the climatic chambers and during the research –
after 8 weeks of storage.
The effect of a temperature of 38+-2 °C and a relative air humidity of 90+-5% did not significantly affect the quality of the barcode prints on the labels. The percentage changes in the average tested barcode parameters are illustrated in charts 1-2, where the decrease or increase in the value of the designated parameter was replaced by values that inform what percentage a given quantity represents in relation to the initial value (initial verification of 100%).
Analyzing the changes in the values of the four coefficients characterizing the quality of barcode prints, it can be stated that the largest differences are observed in the 4th week of storage, in terms of the average bar width deviation – ABD and the reflectance of light from spaces – Rl. A minimal, albeit the largest, thickening of the bar width along with darkening of the background is visible here.
It is impossible to draw definitive conclusions regarding the Rd coefficient due to its variable trend. However, the PCS coefficient changed depending on the changes in the Rd and Rl coefficients. The codes in all analyzed rows were read by the verifier, which proves the high print contrast of the tested samples. Visual assessment of the tested labels also showed no changes in the barcode prints.
The article comes from the magazine “Logistyka”, No. 1/2006.