About Jan and Kevin

About Jan

Born in Holland on 18 October 1948.

Education: Production Engineering and Management Studies

Jan together with his wife Denise started their own company PLASLOPE in 1981 making polyethylene self-seal mailing envelopes and sold it as a going concern in 2010.

In 1981 there was no market for these mailing envelopes in South Africa, as the Postal Authority rules stated that only paper envelopes could be used. After 18 months of negotiations, the approval was given to sell polythene envelopes subject to conditions. Jan can therefore be considered as THE FATHER OF THE PLASTIC MAILING ENVELOPE INDUSTRY IN SOUTH AFRICA.

In 1981 the machines to make Polythene Mailing Envelopes where not available, so production was started with a side seal bag maker and the necessary attachments, which were made in the workshop, at home. With time, other products where developed and implemented using the same equipment that is used to make the envelopes.

When clients realised how efficient the adhesive was, the “self-seal” bags where used as “security bags” which then generated another market. When the criminal found that they could open a self-seal envelope, the search began to find a method to prevent this!

This proved to be impossible, at the time, but a way to leave a visible message if the bag was opened (tampered), was then discovered. The production of Tamper Evident Security Bags then commenced.

There is now an on-going challenge to have a bag with the necessary tamper evident features, which will stay ahead of the criminal, to ensure that the contents of the bag are protected.

Various different applications and markets for these Tamper Evident Security Bags have been developed. Many more challenges will be presented, for which a Tamper Evident Security Bag will be the solution, even if it means that additional features need to be added or the bag needs some unique designing to fit into a system!

The use of self-adhesive tamper evident security seals is another of Jan’s interests. These seals are available in many forms such as those who leave no residue when removed, yet are activated and display the hidden massage when tamper with. Then there are those who have a “partial” transfer which leave a residue. Others cannot be transferred as they fragment when attempts are made to lift them. The sizes and shapes can be designed to suit the application, which together with the visible message and sequential numbering offer fantastic features and opportunities as security seals.

Jan is also involved with the development of systems to firstly stain banknotes inside Tamper evident security bags, ATM cassettes, cross pavement cash security boxes and safes. The need to have an indelible stain is very important, as the criminal has developed means by which they “wash”, some of the stains out of the banknote. This is especially prevalent in the case where smoke type devices or powder dyes are used!

Secondly, as the stained banknotes are being sorted by physical, human inspection and the stain is verified by laboratory examination, this is time consuming and subject to human interpretation and potential inconsistencies. A system is being developed to do both functions by machine, at high speed.

The concept to do this in a banknote validator as used in vending machines has been successfully, demonstrated.

The use of mechanical, security seals (e.g. cable seals, plastic seals and bolt seals, etc) offer another range of features. So Jan’s philosophy is that there are “Horses for courses” and as such the merits of all the available options must be taken into consideration, before the final decision is taken.

Jan has a proven success record in the plastic security bag industry and security seals market which knowledge and experience he is willing to share with companies that are interested.


More About Jan

After finishing my schooling I was not able to go to University due to financial constraints.

My first job was in a laboratory at a foundry, analysing the metal samples and calculating the adjustments which had to be made so that the batch met with a pre-determined specification.

Then a short stay in a microbiological laboratory where we cultivated the bacteria which was used to convert molasses to alcohol.

Ten years at a pharmaceutical company, started in the laboratory (wet analysis), where I set-up the Packaging Materials Quality Control Laboratory. All packaging materials where checked, down to the spelling and decimal points on the labels!

My line of study then changed from Laboratory Technician to Production Management.

I spent some time working as the production planner during which time I drafted “SOP’s” Standard operating procedures for many functions related to production. (These are similar to what is now required for an ISO rating). Thereafter I worked as the Packing Buyer. This involved monitoring stocks of all packaging in relation to the production plans which worked on a period of 6 months.

We needed a blue glass bottle which had a lead-time of 6-9 months! (The only glass factory in the country, detested, changing the glass furnaces to a blue colour!

I wanted to get involved with marketing and sales. So my first job was to represent a company who manufactured aluminium pots and pans and a pressure cooker.

After 18 months I was offered the job in another division which manufactured screw caps for bottles.

A year later I was offered a job with a branch of Hoechst, to sell polythene granules.

Then after 15 months I was promoted to the job of “Market Development, PE films”.

The company’s philosophy was to find opportunities for PE materials which we would then develop in co-operation with the clients who either serviced that market segment, or who had the suitable equipment with which to make the “new” product.

One of my developments was the task of determining the optimum thickness of a refuse bin liner. It involved following a refuse collection truck in two demographically different suburbs in Johannesburg and analysing the reasons why a bin-liner broke, in the collection system which was operated by the council.

We used bags with different thicknesses over a period of 10 weeks.

It was here where I saw a plastic envelope and that was the catalysts which lead to the formation of Plaslope.

It took nearly 2 years of discussion and negotiation with the S.A.Post Office, for them to amend the rules which prohibited any mail to be accepted unless it was packed in paper.

Eventually in a meeting with the deputy Post Master General, I was awarded a provisional approval, subject to several conditions. (You may know that snow seldom falls in Johannesburg, with many years in between when there is no snow and when it does fall it is all cleared by the next morning! Well on my way home from this meeting, it snowed!!!!)

My initial concept was to utilise the spare production capacity at manufacturers which I was privy to from my working with them. I would therefore do the selling etc and submit the orders to the factory for production. I would then deliver the envelopes to the client.

Due to the very short lead-times which the publishers demand, my suppliers were not able to assist, most of the time. Despite me spending long hours in the supplier’s factory, assisting the extrusion and printing departments, the final process on the bag-maker caused many delays.

We then invested in a bag-maker, so that I could control this section better. The product range was then expanded by making “Courier packs” and “Slip-on book covers”.

The following step was to invest in a printing press, so that we could do this work “in-house”.

After investing in more bag-makers we invested in a two-layer co-extruder, so that we could now also make the PE film in-house.

During all of this, we had to find adhesives which would perform well. This resulted in spending lots of “school fees” as we searched for suppliers in South Africa and in Europe. We ended up by sourcing from Europe as the tolerances between the batches, where within acceptable ranges.

I tried to make my own “Tamper Evident Security Tape” as I had become aware of the need for such a tape to be added to the bags which were being used as “security bags”. Many clients had seen how well the adhesive was bonding to the surfaces and assumed that these bags could be used as security bags. What they did not know is that it is possible to break the bond by freezing the adhesive to minus 30C. When the adhesive returns to ambient temperature, it will stick again with the same strength as before. The Tamper Evident Tape can also be opened by freezing, BUT it leaves a visible message, which should draw the attention of the recipient, before he signs for the receipt of the item.

So, we negotiated a license agreement with a company in the UK. But they in turn did not stay abreast with the developments in the marketplace, which necessitated that I cancel the agreement and sign-up with a German, manufacturer.

Now in addition to the Tamper Evident Security Bags, we realised that there is a need for a Tamper Evident Security Seal, in the form of a self-adhesive label. So initially we worked with another company in the UK before switching allegiance to a company in Florida, USA.

I now purchase “jumbo” reels of the Tamper Evident Security label stock from Florida and have it converted into the client’s requirements here in SA.

We import another type of Tamper Evident Security material from a different, German company which I convert into Tamper Evident Security Labels or Seals, using a laser engraving process. This is the same material which motorcar manufacturers use for the “VIN” plates in the car. It will fragment if attempts are made to remove it, which prevents it from being re-positioned. It has incredibly high chemical resistance and temperature properties.

In my years at Plaslope, I often received challenges to design a bag for a unique application.

I enjoyed these challenges which led to the following remarks being made by many people…

“If Jan Visser cannot make it, no one can”

It was a challenge by the largest CIT (Cash in Transit) company in ZA which lead to the formation of Deter-A-Dye Security PTY Ltd.

The CIT company was using a Tamper Evident Security Bag to move banknotes, between its clients and their banks. In an attempt to protect these bags and the money from robbers, the CPC (Cross pavement carrier) was developed. The CPC has an electronic system built-in with many sensors as well as a pyrotechnic device which causes the Tamper Evident bag to shrink and expose its contents. The dye canister then emits a “smoke” (very fine powder) which stains everything it comes into contact with.

The efficiency of this staining is very poor and the SARB (South African Reserve Bank) demanded that the industry either improve this or find alternatives.

I was asked to find a solution, which would comply with the SARB‘s new requirements, but which would still allow the use of the Tamper Evident Security Bag.

In the third meeting, I got the idea and it was patented. However there is now a different fabric which can be used instead of the film which allows the liquid dye stain to be as efficient, without the reliance on the guard’s integrity as is needed in the patented bag.

Linked to this was a demand that the dye which is used must be “Indelible”. No specification was available from the SARB, as to how the dye should be tested to determine that it is “Indelible”. With investigation, I found a document which had been prepared by Scotland Yard. It was a “specification” which after consultation with Forensic science, chemists, was enhanced considerably and is now used as the specification in ZA, for the testing of the resistance of the dye to be washed out of the banknotes.

So, with all of these challenges…. I feel that I have the ability to assist many companies, hence the decision to avail my services as a CONSULTANT!

About Kevin

Having traveled to Taiwan, Hong Kong and China every year over the last 20 odd years and since the wrapping facilities were available i always wrapped my luggage. The problem was that arriving at one’s hotel room, there was no scissors or implement that one could use to take off the wrapping. Trying to phone to ask the help desk or reception from people who could not speak English if they had a pair of scissors was very frustrating and would have to go to reception and draw a picture of what I needed. Of one occasion I had to physically tear it off piece by piece in very humid conditions and  suppliers waiting for me in the lobby. This led me to start developing The BAG SAFE.


After many trials and errors I came up with the design that I was happy with. I then needed to learn about the type of plastic that I needed and started researching and came across Jan Visser who was retired and had a lot of experience in the plastic business. I contacted Jan and set up a meeting. At first he was a bit skeptical, but later realized the potential. So on a hand shake we decided to be 50/50 partners. Jan got samples of different material thicknesses so that we could test them for strength. Jan was also able to advise on double sided tapes that could be used and also offered tamper evident seals that we could use as part of the solution. So after trial after trial especially with the shape and type of perforations needed for the handles I was able to make samples for the medium and large 4 wheel suitcases to prove how it would look and fit. I made a crude wooden jig (picture) to form the rectangular shape needed and used a hand sealing press to seal the 2 flaps created by the jig. Then cut the flaps off with a scissors. Jan was also busy with another project of his own and he arranged a meeting with platen makers and we proceeded to have the platens made. Jan had a roller press which we used to test the process to perforate and die cut The BAG SAFE’S. With some adjustments here and there we got it right. The bottle neck was the manual operation of the jig. We decided to do a run and achieved this at Jan’s premises. We consulted with a machine builder to design a more specific machine to seal and cut in one operation and placed the order. I then made a better wooden jig that I could use to see how it could be incorporated into the heat sealing machine. After a few dimension adjustments this was achieved. I then proceeded to make a metal jig which was scrapped. I then used aluminum and this jig was incorporated into the machine and tested it. We were now ready to do a production run. Next was to finalize the printing design, the retail pack and the retail sleeve describing how to fit The BAG SAFE. We then needed a website and this was created.

It was time to do a stock run using the machine and jig combo and a few tweaks to the packaging and platens. It worked very well.

Later we decided on a few changes to the platen for size and perforation positions and decided on another production run which would be the final product. We also changed the sleeve and the retail bag as well as perfected the folding of The BAG SAFE which ended in a really professional looking product.