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I’m sure you have come across the phrases ‘Chemi-Sealed’, ‘Super Bonded’ and ‘Electronic Lead’ on various Eagle (and Berol) manufactured pencils. Let’s take a quick look at what exactly these are referring to, as well as highlighting the various inception dates.
I’m working off the British registered patents for this post. It may have been that Eagle patented it a touch earlier in the USA, but even if they did, I’d assume the dates would be very close given the wording in the British patent refers to what sounds like a recent invention.
I tend to shy away from adding many American pencil examples onto this blog, but on this occasion I’ve pulled a couple out of the archive for comparison purposes.
You might come across some older Eagle pencils with the phrase ‘Compressed Lead’ stamped on them. I’m not going to cover that in this post because it wasn’t their trademark and its a rather complicated post for another day.
Also, I think certain pencils such as these Eagle Sunbeam below pre-date the various patents and so none of them are stated on the barrel. You will also see a number of more basic Eagle pencils that post-date the patents without the various phrases on them.
Chemi-Sealed
Ok lets get started. The first thing we need to look at it is ‘Chemi-Sealed’. The patent in question is GB391272A, which was published first on 27 April 1933 and with a priority starting on 27 March 1931.
The patent application was actually entitled “Method of making lead pencils and pencils containing other marking material“, and put simply, outlined a preparation method for pencil leads.
I’m not a patent attorney but my general understanding is that even if you haven’t registered the patent, provided you can show that you were using the thing you are looking to patent at an earlier date, the patent office will allow a back date on the registered patent.
We know that pencil leads are glued between the two pieces of wood (see this post for a little lecture on the process), and what Eagle were patenting was the process of treating the leads in such a way that would allow for the leads to stick securely inside the wood barrel.
Eagle proposed to treat the lead cores to remove surface grease. They would then coat the leads with a material which prevented grease within the core from exuding through the coating. This coating would also serve as a binder between the lead and wood.
So why was this necessary? Well according to Eagle, when pencils leads are made, it was normal to include a grease or oily material (such as tallow or stearic acid) into the mix.
This grease would help define the hardness of the pencil core and so was a key component in the recipe.
Problem being, by adding this oily material, you create an issue: the glue that is used to stick the cores to the wood does not react well to the grease, and as such, the bond between both suffers.
What Eagle were trying to do was twofold: firstly, they wanted to remove the greasy surface of the lead, and secondly, once this greasiness was removed, they wanted to create a coating over the lead core which would prevent the grease impregnating the lead from exuding from the interior and impacting the glue bonding it to the wood.
So how did they plan on doing this? According to the patent application, Eagle would use a double treatment of sulphuric acid on the leads which would remove the surface layer of grease on the lead.
Following this, they would wash the leads in water and then immerse the lead in sodium chloride. This process would create a coating that would stop the grease from impacting the glue. Simple really. This process is ‘Chemi-Sealed’.
‘Chemi-Sealed’ also appears on various graded examples of English made Mirado pencils:
So parking the ‘compressed lead’ marked pencils for a second, when looking at age, pencils marked ‘Chemi-Sealed’ only are older than pencils marked ‘Super Bonded’, ‘Electronic Lead’ or a combination of any of the phrases.
The older pencils also tend to have the lettering going from the left to the right (as per my Turquoise 4H photo above) rather than right to the left (as per the advert below).
‘Chemi-Sealed’ through the years (note the 375 item number for Turquoise pencils remained throughout):
‘Chemi-Sealed’ was used right through to the Berol years:
Super Bonded
So what’s ‘Super Bonded’? If we look at the pencils below, we can see that they actually refer us back to the same patent as ‘Chemical-Sealed’. Further, if you look at the Turquoise box further down, ‘Super Bonded’ is in brackets below ‘Chemi-Sealed’.
This all seems to suggest that they are essentially the same thing, or, that the patent can be broken down into its various parts and Eagle simply came up with a name for another part of the process.
If we take a look at the back of the box, we can see that they reference the ‘Chemical-Sealed’ patent specially relating to ‘Super Bonding’:
If I had to hazard a guess I’d think that the ‘Chemical-Sealed’ referred to the acid wash part and the ‘Super Bonded’ referred to the sodium chloride coating.
In truth though, I think it’s probably just all pretty much parts of the same overall process and Eagle just decided to add some more technical sounding words to their advertising.
Interestingly, on the pencils, ‘Superbonded is one single word, whereas on the boxes (such as the half gross box below) it is clearly two words. I think its just lettering squashed together on the pencil rather than a change of heart on the part of Eagle.
However, there was another patent filed by Eagle which is worth drawing your attention to. GB471340A was published on 2 September 1937, with an earliest priority of 14 August 1935. Entitled ‘Improvements in or relating to lead pencils‘, seems to be an extension of the ‘Chemi-Sealed’ patent above.
This particular patent mentions the word ‘bonded’ quite a lot and so I think it wouldn’t be too far a reach to deduce that its publication and the pencils starting to have ‘super bonded’ stamped on them occurred around the same time.
Note the references to both ‘Chemical-Sealed’ and ‘Super Bonded’ on these USA made Back Warriors:
The back of the sleeve actually makes reference to the USA patents for ‘Bonded Lead’. Interesting, but again, we are looking at the UK patents in this post:
Turning back to the patent; Eagle proposed treat the surface of the leads with a miscible and water-soluble glue. Most pencils leads were impregnated in an ordinary non-water-soluble oil or grease. By using the water-soluble glue that mixed with an agent impregnated into the leads, the bonding to the wood was increased.
Eagle’s process involved using a penetrating agent, usually a sulphonated oil or grease, a sulphonated petroleum, a fatty alcohol or naphthol on the leads. This agent was readily miscible with the water-soluble glue used for securing the leads into the wooden barrel.
Fig. 1 from the patent shows a lead about to be assembled into the barrel:
The agent is heated to firstly achieve a low viscosity. Next, the leads are placed in baskets and submerged in the bath until the agent completely penetrates the core.
After removal of the leads from the bath, the leads are allowed to drip dry before being tumbled in heated sawdust, which serves to clean the surface of the lead from the surplus oil or grease. This process prevents the leads from sticking together and they are now ready to be assembled and glued between the segments of a wooden pencil casing.
Fig. 2 is an enlarged transverse sectional view through the completely assembled pencil.
Eagle noted that this new method of lead production required no ‘elaborate apparatus’ or expert care to produce their pencils, thus increasing production speed and reducing cost.
Electronic Lead
Last up, we have patent GB677281A, or to give it it’s full title, “Improvements in or relating to pencils and method of producing same“. In other words ‘Electronic Lead’.
This patent was published on 13 August 1952, however the earliest priority goes back to 14 September 1949. Quite a jump in time since our last two patents, but remember, WWII had been taking place and pencil manufacturing was heavily restricted into the early 1950s. I have a series on that and you can find the first part here .
Eagle gave a rather simplistic explanation on the back of their Turquoise boxes for what this new ‘Electronic Lead’ actually was:
We can also see reference to this patent on the back of certain Mirado boxes:
Note the updated version of the turquoise box and the references to ‘Chemi-Sealed’, ‘Super Bonded’ and ‘Electronic Graphite’. The centre slide box has also been changed to the cheaper flap-top style.
Eagle-eyed will spot that the pencils say ‘Electronic Lead’ whereas the box says ‘Electronic Graphite’. This is just semantics, I think they just ran out of room printing that far down the barrel and went with ‘lead’.
Eagle specially referred to the ‘Chemi-Sealed’ patent when describing this ‘Electronic lead’ process. Essentially they noted that owing to the process whereby a grease impregnated lead is subjected to an acid treatment, a pitted and therefore mechanically weakened lead frequently results.
What Eagle proposed to do therefore was to coat the lead with small crystals (or other solid particles) to which the glue would attach.
Fig. 1 is a diagrammatic view showing the lead impregnating equipment:
Secondly, Eagle proposed to use a form of adhesive that would not be impacted by the grease within the leads or the remnants of any acid remaining due to the “Chemi-Sealed’ process.
The lead was to be bonded to the wood directly throughout the entire length of the pencil with the water-soluble adhesive. Because of this reinforcement and the fact that the lead has not been weakened or pitted due to the acid treatment, Eagle contended that the likelihood of point breakage under normal writing pressure was reduced.
We can see from this version of the Turquoise that Eagle changed ‘Electronic lead’ on the barrel to ‘Electronic Graphite’ to match the box phrase:
Fig. 5 is a cross section showing the graphite bonded to the wood:
So there we are, a bit of a whistle-stop tour of the various phrases you might see on certain Eagle pencils throughout the years. Lets wrap up with a couple of fun American adverts for ‘Chemi-Sealed’ pencils:
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