Here are additional details to help detecting age faking methods, or at least some of then, mentioned under Porcelain Age Faking methods.
Old ceramic body with new decoration This would usually be a decoration newly made on a white, antique porcelain item, or an item with little or unobtrusive decoration. The purpose is to lift its value in the eyes of the buyer, as antique items with decoration are valued higher than plain ones. Can be detected if colors were used that were only available in a period later than when the body was made.
Old bottom and new body Sometimes a line is visible where body and bottom were joined, or the glaze doesn't cover the joint completely. (Please note that some original items like tazzas (stem plate or cup) may show these signs also because the stem or high foot was joined, rather than thrown with the plate or cup, before firing.)Watch for an old bottom attached to a new looking body without any scratches or usage signs.
Fake maritime growth and sediments (shipwreck porcelain) See this example of Nanhai Maritime Archaeology
Acid and glaze deteroriation While glazes can and do deterioriate while buried in soil or lying on the bottom of the sea for extended periods of time, always watch for fake glaze degradation. This can be obtained by immersion in acid. The glaze may look similar as that of shipwreck porcelain. If the whole item has been immersed in acidic liquids, this can show on an unglazed bottom. The bottom will change color and look porous and loose. In some cases sniffing the porcelain can expose this faking method because of the residual smell of chemicals.
Bubbles Two points can help with detecting age faking.
Bubbles direction: Sometimes bubbles are visible through the glaze. They should line up in horizontal strings along the the circumference if the clay was thrown. In items formed by pressing the clay into a mould, the bubbles should form vertical strings. If the bubbles in the clay line up vertically from bottom to top when they should be horizontal instead, this means the clay was pressed into a mould. In such a case check extra carefully if the item could be a modern replica made with mass production methods using moulds.
Bubble size: With ancient manual production methods the clay often contained bubbles of different sizes (visible with magnifier). If bubbles are absent or all uniform and small, this can be a sign of modern production methods. Many of the old ceramics have visible bubbles that show an uneven mix of small and larger ones.
