ANOTHER SIDE OF HUMIDITY IN THE PRESSROOM. SUMMER Part #1

Everybody in the industry knows that proper humidity is essential part of successful printing business. Are there any challenges to manage humidity in the pressroom during summertime?

It’s known that winter time in Canada and in North and North/East of USA is very challenging for pressroom and bindery operations. However, summertime requires even more attention. Very often A/C is necessary to be used through May – August, and it dries air very fast.

A/C condensates the moister from the air and blows dry air to the pressroom and bindery. Actually, It will replicate winter results with all dry air bonuses like paper/board size distortion, web breaks, paper cracking and static build up. If a pressroom has humidification system, the problem is solved. It needs to be run to add water to the dry and cold A/C air.

What happens if A/C works, but a company doesn’t have or “doesn’t need” additional humidification during summer months? Correct! Just open windows and doors and let outside humidity come to the pressroom. It will definitely help with some issues, but will open a can of worms.

As a result of this “innovative” approach, A/C is fighting with outside hot and very humid air. Employees are not happy to work in 100 F, but at the same time, presses are running without web breaks, and static is not gluing 50 lb paper on feeder.

Can we really control internal humidity using outside air in summertime? Yes, we may try)), but even small mistake may lead to failure. Please see the pictures when surplus of outside humidity damaged the products. These labels are result of 2 days with 65% RH (Related Humidity). Outside humidity was 85% RH with 92 F.

Please see the labels with 65%% RH. The product was rejected, it’s not runnable on the customer’s lines.

And 77% RH

Definitely, different paper behaves differently, and experienced Pressroom Manager knows how to balance and what to expect, but it’s extremely tough to maintain stable production environment with limited resources.

Thin stock 40-60 lb. and special paper like metallic paper are the most vulnerable. The same weight stock from different suppliers may react differently, based on cellulose content.I saw multiple cases when changing stock destroyed whole production process, because production didn’t realize that “acceptable humidity window” is different and very narrow.

Example. We used to print labels on well-known metallic paper, the most common at East Coast and Canada. This 70 lb stock was running for years and never created any issues. One day, the customer and sales forces decided to improve the cost. (Sounds very cool)). I tested a skid of the new material. It ran even better than old one, and we achieved 10-15% speed increase. It was early Spring, and temperature and humidity were very stable 23-25 C and 45-50%RH. We didn’t see any paper distortion or curling at the end of the run.

However, having started the first production run, I accompanied by the Pressroom Manager spent THREE shifts trying to make it run. It was so bad: Miss-feed, metallic coating on the rollers and finally – curling final product. Nightmare.

I found the root cause very fast, and it was straightforward.

The “working humidity window” for “cost efficient stock” was very narrow, between 40% RH and 55% RH. when standard stock was running perfectly between 30% RH and 75% RH. “Cost efficient stock” gave us hard time every time when we try to run it without long time acclimatization and perfect press environment.

As a result of cost improvement project, the company lost $5.000 + in idle time and waste in short period of time. Definitely, it may bring some savings in the long run, but pressroom and QA team should be very careful to run this material.

To sum it up:

1. Light stock 40-60 lb. is more sensitive for humidity than regular 70 lb text. It barely can be used in pressroom and bindery without sophisticated and very precise humidification system. In the other case, the waste will be astronomical, min. 10-20%.

2. The stock from different suppliers with the same weight may react differently, based on cellulose content and other specs.

3. “Cost efficient stock” is very sensitive and can be utilized only in very “narrow humidification window”. (therefore it’s so cheap – surprise)). It’s runnable, but pressroom/bindery team should be aware how to make it happen. A/C and precise humidification system are strongly required. In the other case, losses may be more than gain from reduced price.

4. The Sales Team and Customers do not always understand the hidden costs of new “cost efficient solutions” and how much it actually cost for the company.

Based on my experience, I would suggest the next table for offset presses (Heidelberg XL, SM line) and text 80 lb stock (GSM 120 grams – for our European friends)

It’s very easy for DIGITAL Presses (HP, FUJI J, AGFA and XEROX) and text 80lb stock (GSM 120 grams)

I would be very careful with special stock, stock 40-65 lb text (60 -100 GSM), metallic stock and a specially “cost efficient stock”. The humidity window to run it may be very narrow and run waste may be significantly higher than expected.

In the next part, I’ll try to share our strategy and some tricks “how to” reduce waste and produce High Quality Product to the customers.