As a working fabricator, I have to squeeze out the most from every bit of the expendable products that I purchase for my projects, and maximizing yield and performance is paramount in keeping my costs down and elevating my profitability to a higher level.
As a trainer of new fabricators, I also have to stay ahead of the curve when it comes to passing on my knowledge of product and real-life shop situations involving such products as the adhesives used for laminating and seaming, as well as scratch and chip repairs.
I thought that I would share a few things that I have learned and put into practice with regard to glues, and I hope that if you are reading this article, you'll take my advice and put these simple things into practice, too. If you follow my advice, you'll see a marked rise in your glue performance, and a savings in your monthly glue expenses.
First and foremost, remember that most of the glues used in stone installation- including polyester, epoxy, acrylics and cyano-acrylates- most all of these have limited shelf life!
I learned this the hard way a few years ago when I ran short of epoxy, and opened up a unit of glue that was easily three years old. The glue components were stiff and sluggish when mixed, and they never really set up effectively. It was then that I first realized that, "Hey, you'd better check the date produced mark on the can before you start mixing up your glue."
According to a number of glue producers, once glue components have been produced (the date that they are made), they start breaking down. Some slowly, others not so slowly!
This can be crucial if you are depending on the glue joint that you're making to hold a lot of weight, or be under constant tensile pressure (the tensile force that's pulling an assembly apart). If the glue components are degraded from too long a period of storage, the glue will not set and/or cure to the original specifications that it was designed for.
I have found (and I'm sure that there is some chemical engineer that'll want to debate me on my assertion that most, if not all, glues have a limited shelf life) that as a regular fabricator, if I hold to these general assumptions, my glue joints will hold, they'll perform as designed, my customers will be happy, and I will sleep well at night knowing that I did the best job possible for my clients.
That said, another fact that I always share with my students, is that most glues we use are endothermic - which means that they produce heat as they set up and go from a liquid form to a hardened state.
Why is this important? Well, for a number of reasons, glues will set up faster if they are kept in a controlled temperature range. Here's a great example of how this works. Take two identical units of flowing epoxy. One unit is kept at a constant 70 degrees fahrenheit, whilst the other is stored out in the back seat of my trusty pickup truck that sits outside in the Arizona sun all day- everyday. Here in Arizona in the months of June, July, August and September, the interior of a locked pickup truck or car can reach upwards of 200 degrees! Remember that glue kept in the truck can reach that temperature too.
When we mix two batches of glue- one that's been kept at 70 degrees, and the other that was retrieved from my truck interior that was a balmy 200 degrees- which batch do you think will set up first? Of course- the batch that was stored in the 200-degree truck cab, because the individual components (the "A" & "B") had a head start because they were already "hot."
Now, getting your glue to set up fast or faster than normal can be good but it can also be very bad. It can be good if you are in a time crunch and you really need to have your glue set up fast. It can have an undesired side effect, in that the rapid setting time will reduce the cure rate that the glue needs to have in order to develop its designed bond strength.
Let's remember that all glues and cements have what's called an "initial set" and a "cure rate" or "cure time." The initial set time is the amount of time it takes a glue from liquid to hardened state. Once a glue is hard, though, does not necessarily mean that the glue's full bond strength has been achieved. Bond strength is achieved over time; just like concrete needs 28 days on average to reach its full compressive strength, glues, like epoxy in particular, need time to cure as well so that they can reach their designed bond strength.
Why is this important to remember? When I mix glue in an environment that is below the normal recommended temperature (usually below 70 degrees fahrenheit) the glue will take a lot longer to set up and harden. Sometimes the glue will only partially set up- noticeable as almost a "gummy" appearance. In this scenario, the glue will never reach full bond strength - even if you place artificial heat on the piece that you are gluing.
On the other end of the spectrum, if you over heat the piece and the glue components and apply them at an average operating temperature that is above the manufacturer's recommended ranges, you can also affect the glue's performance in a negative way. I just recently discovered this at a student's shop while working on rodding a piece of stone, using their old glue, in their very cold shop. We set up a space heater to safely warm the stone and the glue, and left the warming process on for 8 hours (overnight) and noticed that the next day, the glue that had been used was not bonding well to the stone or the steel rod we were using. In retrospect, we probably used too much heat.
With this in mind, here are some of the things that I have found to help me make my glues work better for me, and last longer:
1. Store all glues and limited shelf life products like glues and sealers in a controlled temperature location. I went on Craigslist and found a refrigerator that could be set at 65 degrees, and that's where I store all of my expendables now.
2. The longer you store glue in your truck (in a hot or cold environment), the shorter the shelf life. Don't let glues freeze, as some polymers will actually change at the molecular level, and render the entire product useless.
3. Keep track of all expiration dates on your glues and sealers. Make a point of using them up before the expiration date rolls around.
4. Mix your glues in an ambient temperature that conforms with the manufacturer's recommended operating temperature. Most glues mix up really well between 70 and 85 degrees. They set well in that range too. If you have to add some heat, use a thermometer to track the temperature. If it gets above 100 degrees, back off on the heat.
Using these simple principals can help you get the most out of your investment of glues and sealers, and help you improve your bottom line.
Until next month...
Best Regards & Happy Fabricating!
"Making Your Glues Work Better and Last Longer" are just some of the topics that are taught each month at AZ School of Rock.
Find out more by logging on to their web site: www.azschoolofrock.com . For more information about class schedules, contact Kevin at 480-309-9422.
Remember that all glues and cements have what's called an "initial set" and a "cure rate" or "cure time." The initial set time is the amount of time it takes a glue to to harden from a liquid state.
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