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As inconceivable as it sounds, this is both the best and worst glue I have ever used.
on 13 May 2015
A review based on use with mortar, bricks and paving slabs.
My mother has a wisteria in a brick planter / rockery, constructed from semi engineering bricks topped with cut paving slabs all the way around. This was built around 3 years ago and all the cut slabs had become loose.
Now in an ideal world, I would have simply removed all the mortar and stuck back down with fresh mortar. The problem with this method is a possibility of breaking a slab when chipping off the mortar and the fact that the slabs she bought at the time were end of the line and are no longer available.
In the past with this sort of situation, I would have just removed the slab dusted the mortar and stuck back down with weather proof exterior PVA glue. I've done this several times over the years and it has always dried solid and firm in a day or two and years later each slab is still stuck down. However, repairing a single loose slab is a rather different prospect to doing several adjoining slabs in one go with PVA. It has no grab and takes an age to set which can easily result in movement and is susceptible to the effects of the weather.
In fact, if I were to have done this I would probably have done one slab per day, waiting for the previous to have dried before doing this next. As such I needed something to do the job that dried quickly to enable me to do it all in one day, and after a little searching I decided upon Gorilla Glue.
Based on my experience with the glue I would offer the following observations.
Gorilla glue is carcinogenic, it does not state this anywhere on the product information about this so be warned.
The glue is a slightly viscous but very runny liquid that looks like Rowse honey, and if you apply the glue vertically it will run, if you apply on the underside of something it will drip.
The best way to describe this glue is to compare it to Soudal fixing foam that's super concentrated and had all the moisture removed that gets activated and foams by adding water. If applied as per the instructions it starts to expand within about 15 mins and continues to do so for over an hour. I strongly advise that you should babysit your work until it is fully cured.
The product description states that the glue expands 3 times its size, the bottle states that it expands to 3-4 times its size, the fact is it expands to more like 6-8 times its size. I used on top of bricks to adhere a slab on top, in this situation a thin bead in the middle of the brick not going within 1" of the edges is the optimal solution.
Anything that the glue comes into contact with while in liquid form (brick, mortar, slabs, skin) will turn black. If you get the glue on anything not intended use white spirit and a nylon brush to remove, this will sadly not prevent black staining but it appears that white spirit makes the glue inert and prevents it from foaming and removes the glue from the surface.
When gluing the 3rd slab down I suffered a glue run which covered almost an entire brick, I managed to clean it off quickly enough, but the brick went black, I tried to jet wash, then scrubbed with soap, then white spirit and in desperation tried muriatic acid twice and nothing worked, I just ended up with a slightly faded and mostly black brick.
When the glue is dry it can be treated in the same way as expanding foam, it can be cut, sanded and filled if required.
SO HOW STRONG IS IT ?
This glue has no initial grab; it is not that sort of glue. The items being glued can easily be manipulated for up to 30-45 mins after applying the glue, I would advise against doing so after 15 mins however, and is rock solid within 2 hours.
Roughly 2 hours after applying I yanked the corner of one of the slabs upwards with all my strength, while I'm no weight lifter at 6'1", a 44" chest and weighing 17 stone I consider myself stronger than average. This amount of force would easily have disjointed a slab laid with mortar, yet the slab held down with gorilla glue did not budge.
Since it has been in place it has suffered torrential rain, 24c direct sunlight and several nights of ground frost and I am glad to say is as secure as the day it dried.
SEPERATING THE GLUE.
The day after I had laid all the slabs back on top of the planter I found that one was uneven, and I did not want to leave it as it was. Being very careful with a 4lb hammer and masons chisel I was able to separate the bond, I started at one end with a few taps, and worked my way around to the other edge and then went back to the start and repeated until it came loose.
Given the strength of the glue I would seriously advise against just taping the chisel through in one place until the slab comes loose as it is a very real possibility that if you do you will crack the slab in half. I would compare it trying to remove a large ceramic tile intact from a wall that has been stuck on with decent adhesive.
Wear gloves, I used a pair of latex gardening gloves and they protected my hands fine, at first I wore a pair of latex gloves underneath but found it was not necessary. If you get any glue on your gloves, pour a tiny bit of white spirit on the glove and rub the palms together and this will prevent transfer to anything you are handling.
Wear a long sleeve top, I did not and even as careful as I was I still got a tiny blob on my arm, if this happens to you use white spirits to remove and then wash with soap and water.
Wear a dust mask, I was using the glue outside in the open and used a P3 mask that filters 99.95% of airborne particles yet still suffered throat irritation for several days after use.
This is a hard one, the adhesive properties of Gorilla glue are undeniable, but not without cost. This stuff is exceptionally hazardous and there is no amount of pressure, money or other incentive that would make me use this indoors ever.
I would strongly advise against using in a situation where should it run, it would ruin the finish of the items being worked on.
Given the same situation again, I would use my old tried and tested method of weather proof PVA for the job, there is just no way that I would consider using this again, the risks just outweigh the benefits it offers.
If I were to review based on my experience I would only give it 3/5, however I can see that it has many useful uses that I would consider it for in future should the need arise. I would go so far as to recommend keeping a small bottle handy in the shed as I can not think of a better product for emergency weatherproofing repairs in the middle of a storm.
As such I am more than happy to give it a 4/5, as it does do nearly everything it says on the tin.
This has admittedly been a rather one sided review based on my use thus far I do hope however that you have found some part of this review of use and I wish you well in your upcoming projects.