TUTORIALS - 1

GLUE
Various types and
how to use them

by Roland Meunier
and Paolo Pizzi

Scale modeling means assembling parts and paint them and obviously the adhesive you use to accomplish the former is THE single most important item in your construction arsenal.. Until a decade ago, there wasn't much choice, basically the only widely available hobby adhesive was tube glue. The real revolution came with the advent of the so-called "superglue" or "krazy glue", instant bonding cyano-acrylic (CA) glue able to provide an unmatched, very strong bond. In recent years, the booming scale model hobby has seen further developments with the introduction of even more specialized types.

What we want to offer you in this article is a panoramic view of the products available on the market with their pros and cons and suggestions on how to make the best of these adhesives in assembling your masterpiece.

TUBE GLUE - If you're not an absolute neophyte, chances are that in your youth you have used countless tubes of glue, often complaining about the obvious deficiencies of this type. When we were kids, there was no alternative and we had to learn how to live with it. Tube glue when compared with other products has only cons: it is messy, the bond it produces isn't very strong and it takes forever to cure. In addition, it attacks plastic and needs to be used sparingly. We have an interesting anecdote regarding Roland's very first kit. He was 6 or 7 when his parents bought him a 1/72 Mirage III kit (presumably from Heller.) He didn't have any experience and the only assistance he could get was from his father, whom, by the way, was no modeler at all. After gluing the fuselage halves together and noticing how the glue did not provide a perfect bond, he used slightly more stuff than necessary when attaching the nose. Result: after 30 seconds, the nose of the Mirage turned into that of the Concorde and a few minutes later the sorry thing looked like the trunk of a depressed elephant.

BOTTOM LINE: Very messy, not very effective, attacks plastic. Why bother when there are better alternatives today?

LIQUID GLUE - Liquid glue became widely available sometimes later. It is still a product you'd want to use in some occasions. For example, when gluing large parts cyano-acrylic adhesive may not be the best solution for it dries too fast and by the time you have finished laying the glue on part B, that on part A may already have fully cured.

In its latest incarnation, Testors' glue comes with a convenient applicator brush. It dries in about two hours. Excess may mar the plastic, even if to a less degree than tube glue: it still needs to be used sparingly. It is VERY toxic and since it contains acetone you should stay away from its fumes (unless you're intentionally trying to "get high" :-) )

PROS - dries slowly, easy to apply
CONS - very toxic, bond is not the strongest
IDEAL USE: to glue large parts like wings and fuselage halves

TENAX 7R - This is a relatively new product which combines the pros of liquid glue with those of superglue, providing a very strong bond without the worries of fast drying time. In fact this glue only reacts under pressure. You typically apply it on the two halves of a fuselage or wing, join the parts, put pressure for about 10 seconds and you get a bond almost as strong as that produced by superglue.

Tenax reacts in a very funny way if mistakenly spilt on a plastic part. It forms a yellowish film which can be easily removed when the glue has fully cured. However, if you touch it while it's still "hot", you'll inevitably mar the plastic. You will need to experiment with this type before you can use it with confidence on your expensive kit. But once you get the grips, it'll become your product of choice when gluing large parts. Tenax is also VERY toxic, be careful when using it.

PROS - cures under pressure allowing for adjustments, very strong bond
CONS - very toxic, not the easiest thing to use, mars the plastic if touched when hot
IDEAL USE: best choice to glue large parts like wings and fuselage halves

TAMIYA EXTRA THIN CEMENT - The latest liquid glue to appear on the market is Tamiya's Extra Thin Cement. It is a refinement of the liquid glue concept and works in a very particular way: you join the parts and brush this stuff on. The capillary action will make the glue seep in the joint and you'll get a very good bond. Curing time is somewhere between 5 and 10 minutes.

This glue is very thin and one of its best features is that apparently it does not attack plastic (well, we haven't actually tried to spill the entire content on a plastic wing and see what happens...) Unlike other liquid adhesives, it leaves virtually no residue, making for exceptionally clean bonds. Though it may still considered poisonous, it does not appear to be as toxic as Testors liquid glue or Tenax and it doesn't small bad.

PROS - you can dry fit first and THEN apply the glue, no residue
CONS - bond is not as strong as that provided by Tenax
IDEAL USE: when the best way to attach parts is to dry-fit them first, excellent for fuselages and wings

FAST-SETTING CA GLUE - The thin, "liquid" stuff is pretty much the original cyano-acrylate, first used during the Vietnam war to quickly patch up wounds before a soldier could get proper medical attention at a MASH. It cures FAST and we really mean fast, in a matter of 2-3 seconds.

Because of its extremely fast curing time, this type of glue is the perfect choice when attaching small parts when no adjustments are needed (e.g. when reliable locators are provided.) Because it is very thin, it is also perfect for inserting adhesive drops to strengthen a weak bond or permanently fix what has been temporarily attached with white glue or similar. Some brands come with a needle-like applicator which is essential to correctly apply this type. If your glue doesn't have one, by all means buy it, it will make your life MUCH easier. Spare applicators are available in most hobby shops. Needless to say, CA glue is also very toxic and if even a tiny drop gets between your fingers, you're in real trouble unless you have a de-bonder.

Speaking of which...one of the funniest stories we've heard about this type of glue is that of a guy building a model while only wearing underpants (presumably in a hot summer.) He allegedly spilt a significant amount of this glue between his crotch and one of his thighs. Moving from the chair to get the de-bonder must have been a particularly painful experience... If this story were true, it would be no laughing matter, yet we feel that this has all the characteristics of a well concocted urban legend. If you spill superglue on plastic parts, don't worry: it can be removed with a few drops of debonder.

PROS - very thin, exceptionally strong bond, cures in 2-3 seconds
CONS - bonds your fingers and possibly other body parts very fast, toxic, needs an applicator and some experience
IDEAL USE: best choice to glue parts when reliable locators are provided, best choice to permanently glue parts that have been temporarily attached with white glue

SLOW-SETTING CA GLUE - This type of cyano-acrylic glue is thicker and has gel-like consistency. It is much easier to apply than the thin stuff: for small applications you can use a toothpick while for larger ones you can apply it out of the bottle via its conical applicator.

This type cures in about 8-10 seconds and while providing the same strong bond as fast-curing CA, it allows for some time to adjust your part(s) until properly positioned/aligned. If you want to freeze the joint before the glue has cured, you can use a CA accelerator, also known as a "kicker". This is the easiest CA glue to use and we particularly recommend it to all beginners. It still bonds your fingers though, but at least you'll have a few seconds before it actually happens...

PROS - easier to use than other types of CA, allows for some time to adjust parts
CONS - because of its thickness excess will be harder to remove, still toxic
IDEAL USE: best choice when a small amount of time (up to 10 secs) is needed to adjust or align parts

GAP-FILLING CA GLUE - Similar to slow-setting CA in that it has the same gel-like consistency, the gap-filling type is a very specialized one. As its name implies, it is used to fill seams and gaps.

This particular type works in conjunction with a CA accelerator (a.k.a. "kicker") and features a very useful two-stage reaction: when the kicker hits gap-filling glue, it freezes it but it does not cure it entirely. This is very useful because regular CA glue would become rock-hard when soaked with the kicker and very difficult to sand. Instead, the gap-filling glue remains slightly softer for at least 20 minutes, plenty of time to sand any excess.

PROS - it doesn't fully cure when hit by a kicker
CONS - slightly more expensive than regular slow-setting CA glue
IDEAL USE: filling seams and (small) gaps

ODORLESS CA GLUE - This is a slow-setting type which does not produce fumes and therefore has virtually no odor. It might be a very expensive luxury if used only because you can't stand the odor of CA glue: this stuff can cost up to 4-5 times as much as regular cyanoacrylate.

The real reason why you want to use this type is that since it produces no fumes, by the same token it doesn't craze clear plastic parts and vacu-formed canopies. There are alternatives to attach clear parts like Microscale's Kristal Klear or the ubiquitous white glue, however none of these can provide a very strong bond.

PROS - no fumes, no odor
CONS - outrageously expensive
IDEAL USE: best for attaching clear plastic or vacu-formed parts

CYANO-ACRYLATE ACCELERATOR (a.k.a. "Kicker") - This product accelerates the reaction of any cyano-acrylic glue and makes it set instantly. It usually comes in a spray bottle and has the consistency and transparency of water. However once again it is a very toxic chemical.

When used in conjunction with regular slow-setting superglue, it is useful to freeze the bond once the correct positioning and/or alignment of parts has been reached. The reaction it produces with gap-filling superglue is slightly different: while it makes the glue solidify, it doesn't fully cure it, thus allowing some 20 minutes or more (depending on brand) for sanding the excess. Because the product comes in a spray bottle, there is usually a lot of waste, hence the product becomes pretty espensive.

PROS - instant bond, solidifies gap-filling CA glue without fully curing it thus allowing for easier sanding
CONS - toxic, expensive
IDEAL USE: to accelerate the reaction of cyanoacrylate

DE-BONDER (a.k.a. "Uncure") - Anyone using cyanoacrylic glue should always keep this stuff within reach. As its name implies, this chemical de-bonds parts attached with CA glue, including of course your fingers or other body parts.

This water-like product works best with fast-setting superglue, leaving virtually no glue residue. However considerable "frosting" will occur. This will be easily washed with water and soap, though if the frosting is inside a hard to reach place it becomes a lot more complicated to remove. With slow-setting or gap-filling superglue, repeated applications may be needed, especially when the glue excess is very thick. Never use it on painted surfaces, it will instantly trash any solvent or water based paint. Once again this is highly-toxic stuff that must be kept away from children.

PROS - de-bonds CA glue
CONS - toxic, does not work as well with thicker CA glue
IDEAL USE: to de-bond parts attached with CA glue

KRISTAL KLEAR - Produced by Microscale, Kristal Klear is yet another very specialized type. It has the consistency and color of white glue but unlike the latter it can perform a little magic: it becomes completely transparent once it cures.

This makes it particularly useful when you need to fill clear parts, as in a closed canopy that doesn't properly align to its sill. Or simply to glue clear parts without incurring in the frosting problem created by CA glue or in the expense of buying an odorless type. It is also useful to simulate glass.

PROS - relatively non-toxic, great to fill clear parts or to simulate glass
CONS - none
IDEAL USE: for attaching or filling clear plastic or vacu-formed parts, to simulate glass

WHITE GLUE - Although Health Central still classifies white glue as a poison because it contains Polyvinyl Acetate (which allegedly can cause gastric and intestinal problems), this glue is in fact harmless and widely used by children in schools. You don't want to know what's inside this stuff unless you don't mind being grossed out...

In scale modeling, white glue has been used since the beginnings of the hobby for  temporary bonding parts or to attach canopies. It can also be used as an airbrush mask. It is easily removed with soapy water. It produces a very weak bond.

PROS - non-toxic (Health Central so sue us :-) ), cheap, widely available, easily removed with soapy water
CONS - produces the weakest bonds
IDEAL USE: for temporary bonds

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