When you start in the model building or mini painting hobbies you will see a lot of different types of glue and other adhesives. The glue section of your friendly local game store can have several brands and types. If you go to a hobby store they might have quite a few more options. If you go to the hardware store they might have an entire aisle devoted to products that join things together. It might be a bit daunting to figure out what will work and what to avoid.
Some glues are great in certain circumstances but almost worthless in others, while some are mediocre in most situations. First I will cover several different types of adhesives you can easily find and then I will cover different types of materials that you can commonly come across while working your way through the hobby.
regardless of what type of glue or material you are using, the most important part of getting things to stick together is proper preparation of the surfaces
In order for two surfaces to stick together with glue it is important to make sure that the surfaces are prepped and ready. Here is a list of things to keep in mind before you put glue to mini.
- Wipe down your parts with a clean cloth: Depending on how long the model has been sitting on your shelf it is just a good idea to get any dust or oil off from it to help the glue come into contact with the model
- Remove paint from join areas: I know that some of you like to paint the parts on the sprue, and unless you are using a brush on primer, you will have primer that covers the joints of your minis. The problem with this is that the glue is bonding to the paint layer rather than the model itself. Many times you won’t have much of an issue, but it can prevent good bonds from forming, this is especially true for plastic model cement because it relies on a reaction with plastic, if the plastic is covered with paint the reaction can’t happen.
- Rough up the surface that you will be gluing: Use a file or sandpaper to slightly rough up the surface of the parts to be glued together. I don’t mean to damage them, just give it a little more texture. This will give the glue more surface area to hold to and will provide a stronger bond between parts. for foam terrain builds use sandpaper or even get out a box knife and cut some very shallow hatch marks on the surfaces to be joined, this will make that stick together much better.
- Large parts may need additional support: Large, hefty parts, especially those that stick out at odd angles, may need some extra support. If you use brass rods, we usually call them pins, you can drill small holes in both sides of a joint and insert the rod to give more physical support and help reduce the number of breaks you experience.
Types of Glue
When you are using a new type of glue, or other adhesive, for the first time. Try it on a piece of scrap material like a sprue in order to see how it works with that type of material and if it has any unanticipated reactions. This will help you to avoid making mistakes that could ruin a perfectly good model.
Plastic Model Glue
This specialized glue is what is called a weld bond glue, it is the best glue for joining plastic parts together. It works through a reaction with the plastic rather than becoming the bond itself. The glue slightly melts the plastic on both sides of the joint, when the reaction stops, the plastic re-solidifies, and the pieces are welded together as one piece.
Plastic glue comes in several thicknesses and even has some that are gap-filling. My personal preference is the Tamiya Extra Thin, a commonly used variety among all model builders. Thin glue can wick into tight spaces and also has a shorter curing time than thicker varieties. the drawback to the extra thin is that it will run much easier and since it is a chemical that reacts with plastic it can ruin the smooth surface of a brand new land raider in a hurry so be careful.
The main drawback to this glue is that it only works with, you guessed it, plastic. If you are putting together a model that has resin, metal, or other materials this glue will be practically useless. Also, it is flammable, so if you are a smoker don’t light up around an open bottle.
Cyanoacrylate, CA Glue, sometimes called super glue or crazy glue will join pretty much any two objects together. It does a good enough job that many mini painters and model makers use it exclusively, that way they don’t have to worry about specialized glue for a job because most of the time this will be just fine. Be careful with thin superglue, it can run and mar the surface of your model. It might not look too bad until you get primer over it, then it is all you can see.
Once set, this glue can be brittle so be careful with your models. Another thing to be super careful about with CA glue is that it can set up almost instantly when exposed to your skin. I can’t even tell you how many times I have glued models together, just to find out that the mini was also glued quite firmly to my hand. Disposable gloves are a good idea to prevent this from happening to you.
There are solvent accelerators for superglue often called kickers. These come in many applicators, sprays, needles, droppers, etc. When applied to liquid superglue they will cause it to set in seconds.
Baking soda is a common household item that reacts with CA glue just like a kicker, but without the nocuous fumes associated with solvents. sprinkling it on the top of CA glue can also create a visual effect like a weld bead.
These have two parts that have the consistency of clay, usually two different colors, that are mixed together when you want to work with them, a resin filler and a hardener. You knead the two parts until you create a new color and can’t see any of the original colors. Once they are mixed together they will have a reaction that will eventually harden and become unworkable. The most common brands in this hobby are Green Stuff and Milliput. Generally, you will mix equal parts together and then you will have quite a while to mold and shape it how you would like. You can adjust the working time by adjusting the amount of the hardener that you use, but this can have an adverse reaction to the end product, it can make it brittle if you use too much, or to never fully set if you use too little. try to just mix up enough for one sitting at a time to avoid wasting too much of it.
I primarily use these to fill gaps in models that don’t quite fit together. It can easily be pressed into the gap and worked with simple modeling tools to match the surface of the model. Many people also commonly use this type of epoxy to sculpt objects for their bases. I have seen people who have sculpted extraordinary items like capes or weapons for their minis out of green stuff and some fine wire to hold it in shape.
Once this is set it can be sanded, painted, filed etc. just like wood or plastic, but since it is technically a resin you will need to use glue that is appropriate for it (see resin below)
This is an air-dry glue that I grew up using in elementary school to glue paper projects together. The most common brand is Elmer’s. This won’t hold your models together, but it is great for lightweight and porous materials. I use it a lot when I am gluing items to the bases of my minis. It dries clear and will shrink in volume once it dries fully. I used it a lot in my tutorial for making a volcanic base. I can be found at most stores including the supermarket. It is water-based, which makes it easy to clean up, non-toxic, and pretty much odorless.
You might not think about this type of glue for our hobby. But once you start to build your own terrain this glue really comes in handy. It has many of the same properties as PVA glue, water-based, non-toxic, easy to clean up when wet. but when you glue extruded foam insulation together with this glue your bond will be really strong. Because it is water-based it doesn’t react with the foam, like solvent-based glues. When it dries it is ridged and will hold the ridged foam together just like it does wood. When it dries you will be more likely to tear the foam than break the glued bond.
This is similar in composition to PVA glue but quite a bit thinner. It dries clear and shrinks like PVA. It is a good solution to sealing projects, particularly the terrain pieces that you want to protect from glues or paints that contain solvents. Spreading this over the top will create a barrier that you can paint over with spray paint without melting your extruded foam creations.
This type of glue has grown in popularity with cosplayers because this type of glue remains flexible but will remain strong. It is used to hold leather or EVA foam together without hampering its ability to flex. However, in the model-making hobby, it is best for gluing dissimilar materials together for things like terrain.
Contact cement is used by applying the glue to both surfaces, then allowing it to dry for a little while to the point that it is quite tacky, then press both sides together. This is solvent-based glue so I would avoid using it to glue extruded insulation foam together unless you have coated it first with something like mod podge.
I generally avoid this in making models and terrain, but I will include it for informational purposes. This glue is highly reactive to temperature. When you purchase the glue it comes in sticks that feel like flexible plastic. When it is forced through the heated glue gun it melts and comes out as a hot thick liquid that cools quickly to go back to the flexible rubber texture. This is a glue to consider for terrain mock-ups but not finished terrain or models. It tends to come apart easily and loses its ability to hold over time.
The right glue for the material
Most materials have something that is best for gluing that material to another object made from the same material. These are what I like best for each of these common modeling materials.
A good weld bond modeling glue will give you the strongest bond for plastic to plastic connections. My preferred brand is Tamiya Extra Thin.
Resin seems to react with a lot of stuff so I try to just go with a good CA glue. I have had good results gluing resin bits with this kind of glue.
CA glue is also a good solution for the size of metal bits that we put together. If you are trying to join large scale metal objects you might try a two part epoxy like JB weld.
Extruded foam insulation
Wood glue is a great solution for extruded foam insulation. It grants a good structure stability as well as being non-toxic and doesn’t interact adversely with the foam.
CA glue is a good solution for holding model parts together that are different materials like resin or metal bits to a plastic main body. Contact cement is great for larger objects that have more surface area like when you are constructing terrain and want to glue an object that you 3D printed to extruded foam or similar.