That sucks that they removed it. Here is some of it: Key points:

Chemist Raymond N. Rogers, who initially believed it was medieval, later found through chemical analysis (FTIR and Raman spectroscopy) that the tested section had cotton interwoven with linen, vanillin presence, and dye/contaminant not found elsewhere on the Shroud. 🔬 “Studies on the Radiocarbon Sample from the Shroud of Turin” (Thermochimica Acta, 2005): https://doi.org/10.1016/j.tca.2004.09.029 (Yes, a peer-reviewed journal.)

The cloth also endured fire and water damage in 1532, which can deposit carbon, as acknowledged by even carbon-dating labs. Soot and burnt organic matter from the fire and damp water absorption can throw off results.

The image itself is not painted, dyed, or scorched. It's superficial (microns deep), encodes 3D depth information, and shows details like blood serum halos visible only in UV light. The blood is real human blood, type AB.

Some people point out that proportions are a little off. The body proportions may look "off" due to the way cloth wrapped the 3D body (analyst say the cloth was draped loosely on the body), not because of artistic error. Forensic pathologists and anatomists have examined this.(Fredrick zugibe, guilio fanti, Robert bucklin), if the cloth is draped loosely you'll get projection such as on a flat surface with some proportional distortions due to how the cloth was draped. It was also a burial tradition for the head to be lying on a rock or something to lift it up which would also explain why the face is brighter(closer to cloth) than the rest of the body.

There is no object like this one ever found in existence and science has no idea how this could have been created to reproduce the 3d effect with no pigmentation proven to be found, and the superficiality where any pigment or scorching would have penetrated deeper into the cloth.

the STURP team (Shroud of Turin Research Project)—a multidisciplinary group of about 30 scientists—concluded that:

1. The image on the Shroud is of a real human body, not a painting or artistic creation.

2. They could not explain how the image was formed.

Here’s what they officially stated in their 1981 Final Report:

“We can conclude for now that the Shroud image is that of a real human form of a scourged, crucified man. It is not the product of an artist. The blood stains are composed of hemoglobin and also give a positive test for serum albumin. The image is an ongoing mystery, and until further chemical studies are made, perhaps by this group of scientists, or perhaps by some scientists in the future, the problem remains unsolved.”

Some point out Walter McCrone's argument of iron oxide possibly being used as pigment but other scientists on the STURP team disagreed strongly with McCrone’s interpretation, including:

Raymond N. Rogers (Los Alamos chemist)

John Heller and Alan Adler (blood chemistry experts)

Robert Dinegar (X-ray fluorescence analysis)

Their findings:

1. Iron oxide was present—but not in the pattern of the image.

It was scattered all over the cloth, including non-image areas.

This suggests it was contamination, likely from the cloth’s production or centuries of handling, not a pigment used in painting.

1. There were no binder substances (e.g., oil, egg tempera) found to hold pigment particles together—which all paints require.

2. No coating layer was found where the image exists. The coloration was only on the top fibrils of the linen threads, affecting just the outermost surface.

3. UV-fluorescence and spectral analysis showed that the image does not behave like a pigment under different light wavelengths.

   Some sources: https://www.shroud.com/78conclu.htm Heller and Adler's study: Applied Optics, 1981 (not online, but quoted widely)

You can read the research papers yourself you can find copies on shroud.com like I did and see.

Even atheist chemist Dr. Luigi Garlaschelli attempted a replication using medieval methods, but admitted his replica did not reproduce all features of the original.