How best to eliminate LP warps

OUTER RING

+1

I use two pizza stones. And put the record in-between. You can probably use glas also.

But use uven instead of sun. The sun is unregulated..

Then you have two factors to adjust. Time and temperature. Start with 40°C and if nothing is happening then bump up some degrees and try again. But probably you don't want to go beyond 50°C.

You don't want to flatten to much either because then you will get radial problems (the grove getting egg shaped. So it is better to have some warp left than "over do it" and get flat and egg shaped. The record that is warped is already destroyed for ever. When vinyl has been prolonged it will not go back to its original shape. Never! Yes it will get flat but the damage is done and it is a longer circumstance on the grove. When vinyl is NOT like a rubber band and goes back to its original shape. It is more as a pizza dough. You will learn that lesson is you have a very warped one and when you have flatten it out.)

When you get a feel of what temperature to use then the procedure is rather straight forward.

(The pizza stone has two disadvantages one is that it will contain moisture that will not be able to escape between the stones and record label can get destroyed. That is eliminated by drying out them in the oven. Next is they're going to scratch the record surface. You need a paper between record and stone or have a simple papper inner sleeve.)

I usually use more time than temperature and may do it over the night when temperature will destroy much faster the record than time.

Good consensus when i wrote 50°C that were in the dial of the oven and don't need be the real temperature..

But yes time is on your side.

@tablejockey 

What’s surprising is how resilient the LP is.

 

Amazing the LP grooves maintain integrity with all the deformation(is that even a word?) going on.

No it is actually not, a wrapped record is stretched but all is depending on how bad the warp is.

The diameter of the grove to the other it is not changed but it is a longer path from for example a stylus at a point the shortest path is the other side of a Hill is a straight line trough it as if it were flat.. but instead the stylus need to travel all the way upp the hill/wrap and down again to the other side.

So the stylus is traveling a LONGER DISTANCE than what it should have been doing when/if the record were flat. But the diameter is still the same.

OK then we have a STRETCHED and longer track then when it were flat (speed variation).

So when we flat out that material the extra length is not shrinking or get shorter back to its original size. The record will again get a new shape..

It will get flat but the additional length in combination that the material has no memory to get back to a previous shape. Where will that extra grove length go?

It will go to the side when we force it by pressure on a flat surface it can not escape somewhere else when it will not shrink.. to the side there is no pressure. 😜

So now we got the extra length on a flat surface so were the warp were it has gone to the side instead and now the third shape we have is that the grove is not circular it is more egg shaped! And do you look att the canteliver/cartridge NOW from the front you will see it work much more side to side (left and right). 

So we have changed from that the cartridge going up and down with the warp to left and right instead.. that is why a wrapped record is in reversible damaged forever. The goal should be to get the record back to its first shape as it comes out from the record press and that goal can we never achieve. Yes we can get the record flat but what does that help us when the circumstances of the grooves are longer than it had when it left the record manufacturers pressing..

Note that of course this is most noticible and easier to see and experience the more warped the record is. And smaller warps you might not be able to notice this at all.. when it is on a much smaller scale.

@lewm 

I think the premise behind flattening the LP by heat and pressure is the hope that the LP WILL return to its original flat shape, that the stretching represented by a warp, if it is indeed stretching, will be eliminated by a corresponding shrinkage.

Yes we might think and hope that shrinkage will happen.

Why should it shrink when we pressure it between two surfaces? It is not rubber.🤔

If you increase one, two or all three of the parameters temperature, pressure or time. It will only result in a bigger and thinner disc an it will never shrink back to its previous shape. Why should it? 🤔

That is exactly what is happening. The disc will be flatt (that is not a problem to achieve) but it's diameter has also increased by a very little bit when we apply as little force and heat we can get away with to just make I flat but the diameter will not magical decrease.

As I said it is small and something probably not something we can easily detect with small warps but the mechanics is the same. But if you have severe warped records you will also be able to flatten them out that part is not a problem to fix.

But you have now instead a severe wobbly grove that is not perfectly circular shaped. Yes you can only convert from one problem (warp) into another (egg shaped). When there is no shrinkage going on..🥰

I have first hand experience with a very warped record that I flatten out carefully over several iterations when I applied pressure and temperature during the whole night for each night and iteration when I did not get it as flat as I expected the first iteration. At the end I got it acceptable flat! (The iterations and time indicated that I didn't use to much heat so that it should destroy the record.) Yes, my happiness over that i had got the record flatter were shortlived when I saw the canteliver and cartridge work like crazy side to side! Never seen something like that in any of my 700 records and I concidered as still unplayable it looked as the needle should be thrown out of the grove, very disturbing. (Remember it were a badly warped record. So less warped will most likely give a less egg deformation). All the efforts was in vain. 🙁

Do you have any experience with record shrinkage? (Smaller warps will give smaller side to side movement but can be still OK and in tolerance, but it is impossible to know if it is little bit worse or not then it were before the warp event.)

Yes, you are right that there is "different" types of warps and severity of them.

The point is to get a better understanding of the material and how it works/act and flattening is not always the end goal and the assumption that we are done and all is going to be back to how it were only if we get it flat.. when there is other things happening and getting worse as a by-product. That we don't concider and take into account that is good that we know of and take it into account. (Oh, this record is to much warped or have a type of warp that makes that individual record "unrepairable" so it can be played again.)

Yeh the server warped disc experience I described before were a great educational thing for me that made me think about what really happened and how it works. When you have bigger warps then it is easier to see the actual effects of the flattening process. When the effects also will be greater.

I went into the project with the mindset that only I straighten it up to flat then all will be good and restored back to its original shape/state as a goal. And did not concidered any other factors that were a mistake from my side that I learned from.

And I probably think that many others also focus on to get it flat and think that it will be 100% restored back to its former shape. (But for smaller warps no one will notice any change or degradation even if they are there.)

Yeh adjusting azimuth ..is something that takes some time to realize how many factors there is..

For example you can dive into the rabbit hole and use for example a azimuth fozgometer or like I did with a digital oscilloscope.

There is many ways/methods to adjust one and each parameter..

Ok here is the kicker if you use one of the tools mentioned above with a calibration LP disc (just a good one of those are pretty pricey in my book) you adjust it perfectly to that individual disc.

But how is a calibration LP disc manufactured? Yes you guessed it. it is manufactured as a LP is usually done. Hopefully with some more care in the setup of the lathe that includes setup of azimuth with the sapphire cutting needles on the lathe that will cut into the lacquer.

So more precise you have just adjusted your azimuth to match the azimuth that the sapphire cutting needle HAD during the initial production of the mold for your specific calibration LP disc..

If you get different manufacturers/labels of calibration LP discs they will not be perfect if you measure those. 

Why.. yes you guessed it there is still some small variance in azimuth setup from sapphire cutting needles setups from lathe to lathe and time to another time.

My approach is when knowing that is to set it perfectly straight like mijostyn have explained.

The reason is to not adjust it after a/one specific lathe cutting occasion, only.

The second reason is that all of the different albums we own has its own lathe azimuth adjustment when they're cut. So the idea is that with a straight setup you will on average over the whole collection be OK. And not be better on some and then worse on some of the others..

In assumption that the cartridge manufacturer has mounted the diamond, canteliver and so on straight..

But the super best way is to get azimuth as good as possible is using one of the tools mentioned and getting different calibration LP discs from of different manufacturers and labels and take a average then maybe you are still little better on it on average.. and probably adjusted also for deviation from the cartridge manufacturer..

Anyway that is nothing that anyone is doing maybe one individual on 2 billion people may or can do that. 🤣

But adjusting VTA/SRA is a different story and has physical properties during cutting. And depending on your stylus shape and so on there is more or less ideal ways to make that adjustment.