The most commonly used glue for making guitars is roughly divided into animal glue and PVC glue. The former is the most traditional. It has been used by humans for thousands of years. This is a chemical glue, which has been developed from the 1960s and has been significantly improved. It is now popular. Look at the difference between them.
Animal glue can be divided into two types, HIDE GLUE and FISH GLUE. HIDE GLUE mainstream is HOT HIDE GLUE (Corresponding to the good hide glue, the shelf life is very short, use with caution). It is necessary to control it yourself before use. Look at the picture below.
This type of hide glue is generally made from pigskin rabbit skin or the like. When tanning, the ratio of glue to water is about 1:2. After stirring for a few hours, it will take a few hours. The glue will completely absorb the water and become gelatinous. It looks very delicious, LOL. Then it needs to be heated and tanning for an hour or two, and it can be used as a liquid. However, after the initial suppression, it is best to spend one night. After cooling, it solidifies again, and the next day it is reheated and used better. Use this thing when you are restrained, look at the picture below.
This is specially used for suede glue. The benefit is that this HIDE GLUE has different strengths. There are from around 50-400. The strength of general instruments is between 100 and 200, depending on the situation. The strength in the above picture is 164, and the figure below is 192.
It is more troublesome to use the hide glue, in addition to the above mentioned need to be pre-tanning. The preparation time is long, and the time for bonding operation is very short, which has a great relationship with room temperature, which is about tens of seconds. Operating time refers to the time it takes for you to prepare the parts to be bonded, apply the hide glue, bond, and clamp the fixture. You may not have a concept. The bonding of some processes is more complicated and may require some auxiliary tools. The working hours of tens of seconds are really short, so it is very skilled to operate.
If the hide glue exceeds the effective working time, it will start to solidify from a viscous liquid. As soon as it begins to solidify, the adhesion will not work. Therefore, be sure to ensure that the glue is still effective before the good fixture. This is also a bit more troublesome. Then, during the tanning process, the maximum temperature should not exceed 145 degrees Fahrenheit. If it exceeds 145 degrees Fahrenheit, the strength of the glue will be destroyed and it will be unusable. The pot in the above picture is able to automatically control the temperature to ensure that the temperature does not exceed this value. Or you can also get a small electric kettle, then put a thermometer inside, manual monitoring, this is more troublesome. As for the difference in strength, the higher the strength of the hide glue, such as 192GRAM, will be shorter than the working time of 164GRAM, that is, the solidification is faster. Therefore, for leather glue of more than 200 strength, the instrument production can not accept such a short operation time, and does not require such high strength. Then there is a more important room temperature to maintain a relatively high temperature. In Shanghai, in the winter, basically the hide glue can not be used for 5 seconds. . . . . It can’t be operated at all. Therefore, it is necessary to open the air conditioner to more than 20 degrees throughout the day. Having said that, is it that HIDE GLUE is too much trouble?
Indeed it is! So now most guitars are made of PVC glue.
Now let’s talk about the advantages of HHG. Such a troublesome glue, the top musical instrument also uses it, there must be an advantage that can not be replaced. That’s right! And there are still many advantages!
1.A very important feature of HHG(Hot Hide Glue ) is that it can perfectly disassemble the bonded wood. After bonding the parts, when you want to disassemble, such as taking off the top, replacing the parts, etc., only need to be heated to the corresponding temperature, the glue can be completely melted, and the joint is opened without damaging the wood. This is a very important performance for the instrument. Because of a guitar, if it is played and maintained well, it can be used for a long time. And with the process of use, often need some repair, replacement, maintenance, etc., it is necessary to open the joint. For example, if the top is cracked, remove the top and fix it, stick the patch inside, and reset the neck. If this PVC glue is used, it is impossible to do it without damaging the wood. Wood fiber must be brought down, which is unacceptable for good instruments.
2.HHG is good for tone. This is because when the skin glue is completely dry, its trait is very hard and hard crystal, does not absorb the energy of vibration, and can perfectly conduct sound. Wherever glue is required to bond, it is a place where energy is easily lost. For example, the joint between the neck and the body, the joint of the sound beam, the joint of the face back and the side panel, and the like. If it is a chemical glue, it will be elastic after it is completely dried and solidified. That will definitely absorb some vibration energy and affect the tone.
3.Timeliness is unlimited, this is more important for a good guitar. If the guitar is made of hide glue, then many years later, as long as the bond is not damaged, its adhesive properties will not decline at all. And when you want to separate, heat up and open the wood without damage, just like fresh hide glue. It is also important to note that completely dry skin glue is not affected by moisture. Even if the humidity is high, the glue will not absorb moisture and will be affected. Imagine that the antique guitars have been repaired countless times, and if they are not used, the glue will be broken.
4.Others have some relatively less important benefits, such as good heat resistance.
The dried hide glue is more heat resistant than modern rubber. For example, in the summer you forget the guitar in the car. The general glue is affected by such high temperature and it is easy to degumming. But the hide glue is fine, only changing to a higher melting temperature will change. For example, it is very good to clean when bonding. When we put a good fixture to clean the residual glue, the glue has turned into a gel-like shape, which is very simple and can be cleaned very cleanly. The other glues are much more troublesome, the surface is cleaned up, and after completely drying, the glue marks can still be seen. There is also a natural rubber, non-toxic and non-polluting.
Let me talk about the advantages of FISH GLUE. Like the hide glue, the glued wood can be opened without damage. But the fish glue n itself is not intended to be used to stick wood. As far as I know, it is used as an emulsifier for the main purpose. Another great benefit is that it works just as well as modern chemical glue. The shape that is usually stored is liquid, and the operation time is long, which is convenient. It is said that there are also a lot of fish glue specially made for musical instruments. But there is a big drawback. That is, when the humidity is too high, the fish gel will absorb moisture and finally open the glue. So it is not recommended for top guitars.
Finally, there are all kinds of modern glue. This PVC, as well as EPOXY epoxy resin. Talk about this PVC glue, which is basically the mainstream glue for musical instrument making or furniture making.
The benefits of modern glue are many, such as long operation time, like this PVC can be no problem for 5 to 10 minutes. Give enough time to adjust and clamp, the glue strength is high, and the glue strength is higher than the animal glue. But here is not very useful for musical instrument production.
When needed, open the lid and use it without any prior preparation. So now 99% of the workshops use this glue. The disadvantage is that it has an adverse effect on the tone, and it is difficult and difficult to handle the wood when it needs to be repaired. Epoxy adhesive has superior adhesion and can be glued to anything. Whether it is wood, metal, leather, etc. But this kind of violent glue, if you want to open it is impossible, can only be completely destroyed. But the advantage of this glue is that it is not water-based, and the wood does not absorb any deformation of moisture when used.
Another type of modern glue is CA glue, which is actually the universal glue we say, like 502.
Operating time varies from a few seconds to a few minutes depending on the viscosity. The benefit is convenience and can be used during some repairs. There are a lot of shortcomings, we will not say more.
In the modern process of making guitar, if you think that the cost of using leather glue is too high, you can consider using this wood glue to make the bonding of most parts. In some places that may need to be repaired after long-term use, it is treated with hide glue, such as the bonding of the bridge to the top, the bonding of the neck to the body, and the bonding of the fingerboard. This brings a lot of benefits to possible repairs in the future. The main thing is that the protection of the piano itself is the best.