Tenor guitar hairline crack

Hello everyone!

I posted last week in the tenor guitar thread here about a hairline crack on a new guitar I've imported from america.

The instrument (to my ears!) plays perfectly and I have no concerns there - there is a little belly to the guitar top, but nothing that looks substantial to me. Currently the restrictions in the UK with covid are quite restrictive, so I don't want to see a luthier yet to get it checked over.

I tried to shine a bright light through the split last night and couldn't see anything. The instrument is almost 100 years old so I just want to be sure it is ok. What are your opinions please?

Attachment 191185

Attachment 191186

100 years old, Wow! I bet it sounds great. If light doesn't get through it, then it's likely a good candidate for thin wicking CA glue to stabilize it. This is best left to someone who knows what they're doing as thin CA is hard to control and will eat any finish it comes in contact with (I mask right up to the crack and use micro tips to put the glue to the crack). When it's safe to get it to a luthier, I'm guessing they'll put some cross-grain cleats on the inside, especially since it's in the soundboard of the instrument. Congrats on finding a cool, old instrument and play it in good health!

It’s the oldest instrument I’ve ever played that’s for sure! It plays so great, I’m so happy with it! :D

Thanks for the advice, so it’s a good idea to get it fixed then! I wasn’t sure if that was normal for something by this old or not.
Thanks so much! :)

If it was me I wouldn't rush to glue that, it might have been there for the last 75 years and be stable. I would make sure the guitar is properly humidified and watch it to see if it changes. If it continues to concern you have a qualified luthier repair it. I wouldn't use CA.

I am with Mike on this, and wouldn't use CA. Mahogany is prone to these cracks, and yours are very small. The one near the bridge does not look recent. I would wait and watch it, while I play it and enjoy it.

Many old instruments have hairline cracks. Your immediate concern is that it does not open up or spread. Use a humidifier such as a Damp-it to ensure the instrument does not dry out too much during the heating season.

When the time comes that you can have it repaired, find a repairman who will use hot hide glue. If your local fretted instrument repair person doesn't like to use hide glue, a good violin repairman can handle the work.

CA is a poor choice for cracks, because if it does not hold, it is very difficult to get a reliable glue joint if an initial repair fails. It is important to understand that CA permanently seals the pores in the wood, and new glue will not stick well to a sealed surface. The old glue must be removed, and it is often not possible to remove the glue without removing wood. The results of this are that what was originally a minor crack turns into a major repair.

I currently have an instrument on the bench that has cracks that were previously glued with CA and have opened up again. I am having to give much thought to how to repair it so it will hold. One of the cracks on that instrument may have to be splinted and carefully touched up, which is a lot of work. This would not have been necessary had the previous repairman used a more suitable glue the first time around. Also, CA can wreak havoc with the finish, and you don't want that, especially on an antique instrument with a finish that is as nice as yours.

If you keep the instrument humidified, the chances that the crack will not spread before you can see a repairman are moderately good.

Hmmm lots of food for thought here, thanks! I will continue to keep an eye on it over the next few months and see if it looks like it changes, then get it inspected and see what the luthier suggests in the way of glue. Are repairs generally obviously visible?!

If hide glue is used, it will look about the same as it does now. Most other glues might darken the crack.
As a matter of fact, it is possible that the crack has already been repaired. If you take the strings loose, see if you can feel any beads or droplets of glue under the crack.

Absolutely wonderful, thank you so much! I will have a look and see what I can feel! :) Thank you!

If you can't feel anything a dental mirror may show glue on the inside, or show glue that was wiped off. That would tell you it has been repaired in the past. You should also be able to see if the crack below the bridge goes all the way thru.